Как сокращенно пишется килограмм

Техническое оформление текста

Как правильно сокращать слова?

Какие требования предъявляются к сокращениям? 

1. Сокращения должны быть понятны читателю. Большое число необщепринятых сокращений затрудняет чтение текста. При усечении слова оставшаяся часть должна позволять легко и безошибочно восстанавливать полное слово, например: филос., филол., не фил.

2. Нежелательны сокращения, совпадающие по написанию с другими. Такие сокращения допустимы только в том случае, если контекст подсказывает, какое именно слово или словосочетание сокращено.

3. Сокращения должны быть единообразными. Принцип единообразия выдерживается, когда сокращаются (или не сокращаются) все однотипные слова. Форма сокращения при этом должна быть одинаковой.

Где найти правила сокращения слов?

• Выдержки из «ГОСТ Р 7.0.12-2011 СИБИД. Библиографическая запись. Сокращение слов и словосочетаний». Общие требования и правила (правила сокращения слов и список наиболее употребительных сокращений) в рубрике «Официальные документы» на нашем портале.

• Правила сокращения слов приводятся в книге А. Э. Мильчина и Л. К. Чельцовой «Справочник издателя и автора» (2-е изд., М., 2003).

Здесь можно найти многие общеупотребительные сокращения:

• Н. Н. Новичков. Словарь современных русских сокращений и аббревиатур. Париж-Москва, 1995;

• Русский орфографический словарь / Под ред. В. В. Лопатина, О. Е. Ивановой. 4-е изд., М., 2012;

• www.sokr.ru — сайт, посвященный сокращениям и аббревиатурам.

Приводим список некоторых общепринятых сокращений:

адм.-терр. административно-территориальный

акад. академик, академия

а. л. и авт. л. авторский лист

а/о акционерное общество, автономный округ, автономная область

б байт

б-ка библиотека

в. век, вв. века

вкз. вокзал

в/о вечернее отделение

вост.-европ. восточноевропейский

г. год; гора

гг. годы; горы

г грамм

г. и г-н господин

гг. и г-да господа

г. и г-жа госпожа

г. и гор. город

гг. города

гос. государственный

гос-во государство

гр. и гр-ка гражданка

гр. и гр-н гражданин

гр-не граждане

деп. департамент; депутат

дисс. диссертация

д. о. и д/о дом отдыха

д/о дневное отделение

дол. долина

долл. доллар

ежедн. ежедневный

ж. и жен. женский

ж. д. и ж/д железная дорога

ж.-д. и ж/д железнодорожный

зап. и з. западный

зап.-европ. западноевропейский

заруб. зарубежный

з. к. и з/к заключенный

з/о заочное отделение

изд-во издательство

ин. и иностр. иностранный

ин-т и инст. институт

и. о. исполняющий обязанности; имя и отчество

и т. д. и так далее

и т. п. и тому подобное, и тому подобные

и т. д. и т. п. и так далее и тому подобное

канд. и к. кандидат

кг килограмм

кг. кегль

м. и муж. мужской

м метр

Мб и Мбайт мегабайт

мб миллибар

мин. министр

мин-во и мин. министерство

мин. и м. минута (Написание этого сокращения с точкой зафиксировано в «Русском орфографическом словаре» РАН; согласно ГОСТу, это сокращение должно быть написано без точки. – Прим. ред.)

мин. и миним. минимальный

мм миллиметр

моск. московский

нед. неделя

п. параграф, пункт

пп. параграфы, пункты

пер. и п. переулок

п/я почтовый ящик

просп., пр. и пр-т проспект

р. и руб. рубль

с. и сек. секунда

с. и стр. страница

см сантиметр

см. смотри

СПб. Санкт-Петербург

т. том, тт. тома

т. и тел. телефон

т. и тов. товарищ

т. и тыс. тысяча

т/к телеканал

ул. улица

Ф. И. О. и ф. и. о. фамилия, имя, отчество

ч. час (Написание этого сокращения с точкой зафиксировано в «Русском орфографическом словаре» РАН; согласно ГОСТу, это сокращение должно быть написано без точки. – Прим. ред.)

003 Миллиметр мм mm ММ MMT 004 Сантиметр см cm СМ CMT 005 Дециметр дм dm ДМ DMT 006 Метр м m М MTR 008 Километр; тысяча метров км; 10³ м km КМ; ТЫС М KMT 009 Мегаметр; миллион метров Мм; 10⁶ м Mm МЕГАМ; МЛН М MAM 018 Погонный метр пог. м ПОГ М 019 Тысяча погонных метров 10³ пог. м ТЫС ПОГ М 020 Условный метр усл. м УСЛ М 039 Дюйм (25,4 мм) дюйм in ДЮЙМ INH 041 Фут (0,3048 м) фут ft ФУТ FOT 043 Ярд (0,9144 м) ярд yd ЯРД YRD 047 Морская миля (1852 м) миля n mile МИЛЬ NMI 048 Тысяча условных метров 10³ усл. м ТЫС УСЛ М 049 Километр условных труб км усл. труб КМ УСЛ ТРУБ 050 Квадратный миллиметр мм² mm² ММ2 MMK 051 Квадратный сантиметр см² cm² СМ2 CMK 053 Квадратный дециметр дм² dm² ДМ2 DMK 054 Тысяча квадратных дециметров 10³ дм² ТЫС ДМ2 055 Квадратный метр м² m² М2 MTK 056 Миллион квадратных дециметров 10⁶ дм² МЛН ДМ2 057 Миллион квадратных метров 10⁶ м² МЛН М2 058 Тысяча квадратных метров 10³ м² daa ТЫС М2 DAA 059 Гектар га ha ГА HAR 060 Тысяча гектаров 10³ га ТЫС ГА 061 Квадратный километр км² km² КМ2 KMK 062 Условный квадратный метр усл. м² УСЛ М2 063 Тысяча условных квадратных метров 10³ усл. м² ТЫС УСЛ М2 064 Миллион условных квадратных метров 10⁶ усл. м² МЛН УСЛ М2 071 Квадратный дюйм (645,16 мм2) дюйм² in² ДЮЙМ2 INK 073 Квадратный фут (0,092903 м2) фут² ft² ФУТ2 FTK 075 Квадратный ярд (0,8361274 м2) ярд² yd² ЯРД2 YDK 081 Квадратный метр общей площади м² общ. пл М2 ОБЩ ПЛ 082 Тысяча квадратных метров общей площади 10³ м² общ. пл ТЫС М2 ОБЩ ПЛ 083 Миллион квадратных метров общей площади 10⁶ м² общ. пл МЛН М2. ОБЩ ПЛ 084 Квадратный метр жилой площади м² жил. пл М2 ЖИЛ ПЛ 085 Тысяча квадратных метров жилой площади 10³ м² жил. пл ТЫС М2 ЖИЛ ПЛ 086 Миллион квадратных метров жилой площади 10⁶ м² жил. пл МЛН М2 ЖИЛ ПЛ 087 Квадратный метр учебно-лабораторных зданий м² уч. лаб. здан М2 УЧ.ЛАБ ЗДАН 088 Тысяча квадратных метров учебно-лабораторных зданий 10³ м² уч. лаб. здан ТЫС М2 УЧ. ЛАБ ЗДАН 089 Миллион квадратных метров в двухмиллиметровом исчислении 10⁶ м² 2 мм исч МЛН М2 2ММ ИСЧ 109 Ар (100 м2) а a АР ARE 110 Кубический миллиметр мм³ mm³ ММ3 MMQ 111 Кубический сантиметр; миллилитр см³; мл cm³; ml СМ3; МЛ CMQ; MLT 112 Литр; кубический дециметр л; дм³ I; L; dm³ Л; ДМ3 LTR; DMQ 113 Кубический метр м³ m3 М3 MTQ 114 Тысяча кубических метров 10³ м³ ТЫС М3 115 Миллиард кубических метров 10⁹ м³ МЛРД М3 116 Декалитр дкл ДКЛ 118 Децилитр дл dl ДЛ DLT 119 Тысяча декалитров 10³ дкл ТЫС ДКЛ 120 Миллион декалитров 10⁶ дкл МЛН ДКЛ 121 Плотный кубический метр плотн. м³ ПЛОТН М3 122 Гектолитр гл hl ГЛ HLT 123 Условный кубический метр усл. м³ УСЛ М3 124 Тысяча условных кубических метров 10³ усл. м³ ТЫС УСЛ М3 125 Миллион кубических метров переработки газа 10⁶ м³ пере-раб. газа МЛН М3 ПЕРЕРАБ ГАЗА 126 Мегалитр Мл Ml МЕГАЛ MAL 127 Тысяча плотных кубических метров 10³ плотн. м³ ТЫС ПЛОТН М3 128 Тысяча полулитров 10³ пол. л ТЫС ПОЛ Л 129 Миллион полулитров 10⁶ пол. л МЛН ПОЛ Л 130 Тысяча литров; 1000 литров 10³ л; 1000 л ТЫС Л 131 Кубический дюйм (16387,1 мм3) дюйм³ in3 ДЮЙМ3 INQ 132 Кубический фут (0,02831685 м3) фут³ ft3 ФУТ3 FTQ 133 Кубический ярд (0,764555 м3) ярд³ yd3 ЯРД3 YDQ 159 Миллион кубических метров 10⁶ м³ 10⁶ m3 МЛН М3 HMQ 160 Гектограмм гг hg ГГ HGM 161 Миллиграмм мг mg МГ MGM 162 Метрический карат (1 карат=200 мг=2.10[-4*] кг) кар МС КАР CTM 163 Грамм г g Г GRM 164 Микрограмм 165 Тысяча каратов метрических 10³ кар ТЫС КАР 166 Килограмм кг kg КГ KGM 167 Миллион каратов метрических 10⁶ кар МЛН КАР 168 Тонна; метрическая тонна (1000 кг) т t Т TNE 169 Тысяча тонн 10³ т ТЫС Т 170 Килотонна 10³ т kt КТ KTN 171 Миллион тонн 10⁶ т МЛН Т 172 Тонна условного топлива т усл. топл Т УСЛ ТОПЛ 173 Сантиграмм сг cg СГ CGM 175 Тысяча тонн условного топлива 10³ т усл. топл ТЫС Т УСЛ ТОПЛ 176 Миллион тонн условного топлива 10⁶ т усл. топл МЛН Т УСЛ ТОПЛ 177 Тысяча тонн единовременного хранения 10³ т единовр. хран ТЫС Т ЕДИНОВР ХРАН 178 Тысяча тонн переработки 10³ т перераб ТЫС Т ПЕРЕРАБ 179 Условная тонна усл. т УСЛ Т 181 Брутто-регистровая тонна (2,8316 м[3*]) БРТ — БРУТТ. РЕГИСТР Т GRT 185 Грузоподъемность в метрических тоннах т грп — Т ГРУЗОПОД CCT 206 Центнер (метрический) (100 кг); гектокилограмм; квинтал[*] (метрический); децитоннах ц q; 10² kg Ц DTN 207 Тысяча центнеров 10³ ц ТЫС Ц 212 Ватт Вт W ВТ WTT 214 Киловатт кВт kW КВТ KWT 215 Мегаватт; тысяча киловатт 10³ кВт ТЫС КВТ 222 Вольт В V В VLT 223 Киловольт кВ kV КВ KVT 226 Вольт-ампер В.А В.А 227 Киловольт-ампер кВ.А kV.A КВ.А KVA 228 Мегавольт-ампер (тысяча киловольт-ампер) МВ.А MV.A МЕГАВ.А MVA 230 Киловар квар kVAR КВАР KVR 231 Метр в час м/ч М/Ч 232 Килокалория ккал ККАЛ 233 Гигакалория Гкал ГИГАКАЛ 234 Тысяча гигакалорий 10³ Гкал ТЫС ГИГАКАЛ 235 Миллион гигакалорий 10⁶ Гкал МЛН ГИГАКАЛ 236 Калория в час кал/ч КАЛ/Ч 237 Килокалория в час ккал/ч ККАЛ/Ч 238 Гигакалория в час Гкал/ч ГИГАКАЛ/Ч 239 Тысяча гигакалорий в час 10³ Гкал/ч ТЫС ГИГАКАЛ/Ч 241 Миллион ампер-часов 10⁶ А.ч МЛН А.Ч 242 Миллион киловольт-ампер 10⁶ кВ.А МЛН КВ.А 243 Ватт-час Вт.ч W.h ВТ.Ч WHR 245 Киловатт-час кВт.ч kW.h КВТ.Ч KWH 246 Мегаватт-час; 1000 киловатт-часов МВт.ч; 10³ кВт.ч МW.h МЕГАВТ.Ч; ТЫС КВТ.Ч MWH 247 Гигаватт-час (миллион киловатт-часов) ГВт.ч GW.h ГИГАВТ.Ч GWH 248 Киловольт-ампер реактивный кВ.А Р КВ.А Р 249 Миллиард киловатт-часов 10⁹ кВт.ч МЛРД КВТ.Ч 250 Тысяча киловольт-ампер реактивных 10³ кВ.А Р ТЫС КВ.А Р 251 Лошадиная сила л. с ЛС 252 Тысяча лошадиных сил 10³ л. с ТЫС ЛС 253 Миллион лошадиных сил 10⁶ л. с МЛН ЛС 254 Бит бит БИТ 255 Байт бай БАЙТ 256 Килобайт кбайт КБАЙТ 257 Мегабайт Мбайт МБАЙТ 258 Бод бод БОД 260 Ампер А A А AMP 263 Ампер-час (3,6 кКл) А.ч A.h А.Ч AMH 264 Тысяча ампер-часов 10³ А.ч 10³ A.h ТЫС А.Ч TAH 270 Кулон Кл C КЛ COU 271 Джоуль Дж J ДЖ JOU 273 Килоджоуль кДж kJ КДЖ KJO 274 Ом Ом <омега> ОМ OHM 280 Градус Цельсия град. C град. C ГРАД ЦЕЛЬС CEL 281 Градус Фаренгейта град. F град. F ГРАД ФАРЕНГ FAN 282 Кандела кд cd КД CDL 283 Люкс лк lx ЛК LUX 284 Люмен лм lm ЛМ LUM 287 Генри Гн ГН 288 Кельвин K K К KEL 289 Ньютон Н N Н NEW 290 Герц Гц Hz ГЦ HTZ 291 Килогерц кГц kHz КГЦ KHZ 292 Мегагерц МГц MHz МЕГАГЦ MHZ 294 Паскаль Па Pa ПА PAL 296 Сименс См S СИ SIE 297 Килопаскаль кПа kPa КПА KPA 298 Мегапаскаль МПа MPa МЕГАПА MPA 300 Физическая атмосфера (101325 Па) атм atm АТМ ATM 301 Техническая атмосфера (98066,5 Па) ат at АТТ ATT 302 Гигабеккерель ГБк GBq ГИГАБК GBQ 303 Килобеккерель 304 Милликюри мКи mCi МКИ MCU 305 Кюри Ки Ci КИ CUR 306 Грамм делящихся изотопов г Д/И g fissile isotopes Г ДЕЛЯЩ ИЗОТОП GFI 307 Мегабеккерель 308 Миллибар мб mbar МБАР MBR 309 Бар бар bar БАР BAR 310 Гектобар гб hbar ГБАР HBA 312 Килобар кб kbar КБАР KBA 313 Тесла Тл ТЛ 314 Фарад Ф F Ф FAR 316 Киллограмм на кубический метр кг/м³ kg/m³ КГ/М3 KMQ 317 Килограмм на квадратный сантиметр кг/см² КГ/СМ2 320 Моль 323 Беккерель Бк Bq БК BQL 324 Вебер Вб Wb ВБ WEB 327 Узел (миля/ч) уз kn УЗ KNT 328 Метр в секунду м/с m/s М/С MTS 330 Оборот в секунду об/с r/s ОБ/С RPS 331 Оборот в минуту об/мин r/min ОБ/МИН RPM 333 Километр в час км/ч km/h КМ/Ч KMH 335 Метр на секунду в квадрате м/с² m/s² М/С2 MSK 337 Миллиметр водяного столба мм вод. ст ММ ВОД СТ 338 Миллиметр ртутного столба мм рт. ст ММ РТ СТ 339 Сантиметр водяного столба см вод. ст СМ ВОД СТ 340 Грамм условного топлива на киловатт-час г у.т/кВт-ч Г У.Т./КВТ-Ч 341 Килограмм условного топлива на гигакалорию кг у.т./Гкал КГ У.Т./ГКАЛ 349 Кулон на килограмм Кл/кг C/kg КЛ/КГ CKG 352 Микросекунда мкс МКС 353 Миллисекунда млс МЛС 354 Секунда с s С SEC 355 Минута мин min МИН MIN 356 Час ч h Ч HUR 359 Сутки сут; дн d СУТ; ДН DAY 360 Неделя нед — НЕД WEE 361 Декада дек — ДЕК DAD 362 Месяц мес — МЕС MON 364 Квартал кварт — КВАРТ QAN 365 Полугодие полгода — ПОЛГОД SAN 366 Год г; лет a ГОД; ЛЕТ ANN 368 Десятилетие деслет — ДЕСЛЕТ DEC 383 Рубль руб РУБ 384 Тысяча рублей 10³ руб ТЫС РУБ 385 Миллион рублей 10⁶ руб МЛН РУБ 386 Миллиард рублей 10⁹ руб МЛРД РУБ 387 Триллион рублей 10¹² руб ТРИЛЛ РУБ 388 Квадрильон рублей 10¹⁵ руб КВАДР РУБ 414 Пассажиро-километр пасс.км ПАСС.КМ 421 Пассажирское место (пассажирских мест) пасс. мест ПАСС МЕСТ 423 Тысяча пассажиро-километров 10³пасс.км ТЫС ПАСС.КМ 424 Миллион пассажиро-километров 10⁶ пасс. км МЛН ПАСС.КМ 427 Пассажиропоток пасс.поток ПАСС.ПОТОК 449 Тонно-километр т.км Т.КМ 450 Тысяча тонно-километров 10³ т.км ТЫС Т.КМ 451 Миллион тонно-километров 10⁶ т. км МЛН Т.КМ 479 Тысяча наборов 10³ набор ТЫС НАБОР 499 Килограмм в секунду кг/с — КГ/С KGS 508 Тысяча метров кубических в час 509 Километр в сутки км/сут КМ/СУТ 510 Грамм на киловатт-час г/кВт.ч Г/КВТ.Ч 511 Килограмм на гигакалорию кг/Гкал КГ/ГИГАКАЛ 512 Тонно-номер т.ном Т.НОМ 513 Автотонна авто т АВТО Т 514 Тонна тяги т.тяги Т ТЯГИ 515 Дедвейт-тонна дедвейт.т ДЕДВЕЙТ.Т 516 Тонна-танид т.танид Т.ТАНИД 521 Человек на квадратный метр чел/м² ЧЕЛ/М2 522 Человек на квадратный километр чел/км² ЧЕЛ/КМ2 533 Тонна пара в час т пар/ч — Т ПАР/Ч TSH 534 Тонна в час т/ч Т/Ч 535 Тонна в сутки т/сут Т/СУТ 536 Тонна в смену т/смен Т/СМЕН 537 Тысяча тонн в сезон 10³ т/сез ТЫС Т/СЕЗ 538 Тысяча тонн в год 10³ т/год ТЫС Т/ГОД 539 Человеко-час чел.ч ЧЕЛ.Ч 540 Человеко-день чел.дн ЧЕЛ.ДН 541 Тысяча человеко-дней 10³ чел.дн ТЫС ЧЕЛ.ДН 542 Тысяча человеко-часов 10³ чел.ч ТЫС ЧЕЛ.Ч 543 Тысяча условных банок в смену 10³ усл. банк/смен ТЫС УСЛ БАНК/СМЕН 544 Миллион единиц в год 10⁶ ед/год МЛН ЕД/ГОД 545 Посещение в смену посещ/смен ПОСЕЩ/СМЕН 546 Тысяча посещений в смену 10³ посещ/смен ТЫС ПОСЕЩ/ СМЕН 547 Пара в смену пар/смен ПАР/СМЕН 548 Тысяча пар в смену 10³ пар/смен ТЫС ПАР/СМЕН 550 Миллион тонн в год 10⁶ т/год МЛН Т/ГОД 552 Тонна переработки в сутки т перераб/сут Т ПЕРЕРАБ/СУТ 553 Тысяча тонн переработки в сутки 10³ т перераб/сут ТЫС Т ПЕРЕРАБ/СУТ 554 Центнер переработки в сутки ц перераб/сут Ц ПЕРЕРАБ/СУТ 555 Тысяча центнеров переработки в сутки 10³ ц перераб/сут ТЫС Ц ПЕРЕРАБ/СУТ 556 Тысяча голов в год 10³ гол/год ТЫС ГОЛ/ГОД 557 Миллион голов в год 10⁶ гол/год МЛН ГОЛ/ГОД 558 Тысяча птицемест 10³ птицемест ТЫС ПТИЦЕ-МЕСТ 559 Тысяча кур-несушек 10³ кур. несуш ТЫС КУР. НЕСУШ 561 Тысяча тонн пара в час 10³ т пар/ч ТЫС Т ПАР/Ч 562 Тысяча прядильных веретен 10³ пряд.верет ТЫС ПРЯД ВЕРЕТ 563 Тысяча прядильных мест 10³ пряд.мест ТЫС ПРЯД МЕСТ 596 Кубический метр в секунду м³/с m3/s М3/С MQS 598 Кубический метр в час м³/ч m3/h М3/Ч MQH 599 Тысяча кубических метров в сутки 10³ м³/сут — ТЫС М3/СУТ TQD 616 Бобина боб — БОБ NBB 625 Лист л. — ЛИСТ LEF 626 Сто листов 100 л. — 100 ЛИСТ CLF 630 Тысяча стандартных условных кирпичей тыс станд. усл. кирп — ТЫС СТАНД УСЛ КИРП MBE 639 Доза доз ДОЗ 640 Тысяча доз 10³ доз ТЫС ДОЗ 641 Дюжина (12 шт.) дюжина Doz; 12 ДЮЖИНА DZN 642 Единица ед ЕД 643 Тысяча единиц 10³ ед ТЫС ЕД 644 Миллион единиц 10⁶ ед МЛН ЕД 657 Изделие изд — ИЗД NAR 661 Канал канал КАНАЛ 673 Тысяча комплектов 10³ компл ТЫС КОМПЛ 683 Сто ящиков 100 ящ. Hbx 100 ЯЩ HBX 698 Место мест МЕСТ 699 Тысяча мест 10³ мест ТЫС МЕСТ 704 Набор набор — НАБОР SET 709 Тысяча номеров 10³ ном ТЫС НОМ 715 Пара (2 шт.) пар pr; 2 ПАР NPR 724 Тысяча гектаров порций 10³ га порц ТЫС ГА ПОРЦ 728 Пачка пач ПАЧ 729 Тысяча пачек 10³ пач ТЫС ПАЧ 730 Два десятка 20 20 2 ДЕС SCO 732 Десять пар 10 пар — ДЕС ПАР TPR 733 Дюжина пар дюжина пар — ДЮЖИНА ПАР DPR 734 Посылка посыл — ПОСЫЛ NPL 735 Часть часть — ЧАСТЬ NPT 736 Рулон рул — РУЛ NPL 737 Дюжина рулонов дюжина рул — ДЮЖИНА РУЛ DRL 740 Дюжина штук дюжина шт — ДЮЖИНА ШТ DPC 744 Процент % ПРОЦ 745 Элемент элем CI ЭЛЕМ NCL 746 Промилле (0,1 процента) промилле ПРОМИЛЛЕ 751 Тысяча рулонов 10³ рул ТЫС РУЛ 761 Тысяча станов 10³ стан ТЫС СТАН 762 Станция станц СТАНЦ 775 Тысяча тюбиков 10³ тюбик ТЫС ТЮБИК 776 Тысяча условных тубов 10³ усл.туб ТЫС УСЛ ТУБ 778 Упаковка упак — УПАК NMP 779 Миллион упаковок 10⁶ упак МЛН УПАК 780 Дюжина упаковок дюжина упак — ДЮЖИНА УПАК DZP 781 Сто упаковок 100 упак — 100 УПАК CNP 782 Тысяча упаковок 10³ упак ТЫС УПАК 792 Человек чел ЧЕЛ 793 Тысяча человек 10³ чел ТЫС ЧЕЛ 794 Миллион человек 10⁶ чел МЛН ЧЕЛ 796 Штука шт pc; 1 ШТ PCE; NMB 797 Сто штук 100 шт 100 100 ШТ CEN 798 Тысяча штук тыс. шт; 1000 шт 1000 ТЫС ШТ MIL 799 Миллион штук 10⁶ шт 10⁶ МЛН ШТ MIO 800 Миллиард штук 10⁹ шт 10⁹ МЛРД ШТ MLD 801 Биллион штук (Европа); триллион штук 10¹² шт 10¹² БИЛЛ ШТ (ЕВР); ТРИЛЛ ШТ BIL 802 Квинтильон штук (Европа) 10¹⁸ шт 10¹⁸ КВИНТ ШТ TRL 808 Миллион экземпляров 10⁶ экз МЛН ЭКЗ 810 Ячейка яч ЯЧ 812 Ящик ящ ЯЩ 820 Крепость спирта по массе креп. спирта по массе % mds КРЕП СПИРТ ПО МАССЕ ASM 821 Крепость спирта по объему креп. спирта по объему % vol КРЕП СПИРТ ПО ОБЪЕМ ASV 831 Литр чистого (100 %) спирта л 100% спирта — Л ЧИСТ СПИРТ LPA 833 Гектолитр чистого (100 %) спирта Гл 100% спирта — ГЛ ЧИСТ СПИРТ HPA 836 Голова гол ГОЛ 837 Тысяча пар 10³ пар ТЫС ПАР 838 Миллион пар 10⁶ пар МЛН ПАР 839 Комплект компл КОМПЛ 840 Секция секц СЕКЦ 841 Килограмм пероксида водорода кг H2О2 — КГ ПЕРОК-СИД ВОДО-РОДА — 845 Килограмм 90 %-го сухого вещества кг 90% с/в — КГ 90 ПРОЦ СУХ ВЕЩ KSD 847 Тонна 90 %-го сухого вещества т 90% с/в — Т 90 ПРОЦ СУХ ВЕЩ TSD 852 Килограмм оксида калия кг К2О — КГ ОКСИД КАЛИЯ KPO 859 Килограмм гидроксида калия кг КОН — КГ ГИДРО-КСИД КА-ЛИЯ KPH 861 Килограмм азота кг N — КГ АЗОТ KNI 863 Килограмм гидроксида натрия кг NaOH — КГ ГИДРО-КСИД НАТРИЯ KSH 865 Килограмм пятиокиси фосфора кг Р2О5 — КГ ПЯТИ-ОКИСЬ ФОСФОРА KPP 867 Килограмм урана кг U — КГ УРАН KUR 868 Бутылка бут БУТ 869 Тысяча бутылок 10³ бут ТЫС БУТ 870 Ампула ампул АМПУЛ 871 Тысяча ампул 10³ ампул ТЫС АМПУЛ 872 Флакон флак ФЛАК 873 Тысяча флаконов 10³ флак ТЫС ФЛАК 874 Тысяча тубов 10³ туб ТЫС ТУБ 875 Тысяча коробок 10³ кор ТЫС КОР 876 Условная единица усл. ед УСЛ ЕД 877 Тысяча условных единиц 10³ усл. ед ТЫС УСЛ ЕД 878 Миллион условных единиц 10⁶ усл. ед МЛН УСЛ ЕД 879 Условная штука усл. шт УСЛ ШТ 880 Тысяча условных штук 10³ усл. шт ТЫС УСЛ ШТ 881 Условная банка усл. банк УСЛ БАНК 882 Тысяча условных банок 10³ усл. банк ТЫС УСЛ БАНК 883 Миллион условных банок 10⁶ усл. банк МЛН УСЛ БАНК 884 Условный кусок усл. кус УСЛ КУС 885 Тысяча условных кусков 10³ усл. кус ТЫС УСЛ КУС 886 Миллион условных кусков 10⁶ усл. кус МЛН УСЛ КУС 887 Условный ящик усл. ящ УСЛ ЯЩ 888 Тысяча условных ящиков 10³ усл. ящ ТЫС УСЛ ЯЩ 889 Условная катушка усл. кат УСЛ КАТ 890 Тысяча условных катушек 10³ усл. кат ТЫС УСЛ КАТ 891 Условная плитка усл. плит УСЛ ПЛИТ 892 Тысяча условных плиток 10³ усл. плит ТЫС УСЛ ПЛИТ 893 Условный кирпич усл. кирп УСЛ КИРП 894 Тысяча условных кирпичей 10³ усл. кирп ТЫС УСЛ КИРП 895 Миллион условных кирпичей 10⁶ усл. кирп МЛН УСЛ КИРП 896 Семья семей СЕМЕЙ 897 Тысяча семей 10³ семей ТЫС СЕМЕЙ 898 Миллион семей 10⁶ семей МЛН СЕМЕЙ 899 Домохозяйство домхоз ДОМХОЗ 900 Тысяча домохозяйств 10³ домхоз ТЫС ДОМХОЗ 901 Миллион домохозяйств 10⁶ домхоз МЛН ДОМХОЗ 902 Ученическое место учен. мест УЧЕН МЕСТ 903 Тысяча ученических мест 10³ учен. мест ТЫС УЧЕН МЕСТ 904 Рабочее место раб. мест РАБ МЕСТ 905 Тысяча рабочих мест 10³ раб. мест ТЫС РАБ МЕСТ 906 Посадочное место посад. мест ПОСАД МЕСТ 907 Тысяча посадочных мест 10³ посад. мест ТЫС ПОСАД МЕСТ 908 Номер ном НОМ 909 Квартира кварт КВАРТ 910 Тысяча квартир 10³ кварт ТЫС КВАРТ 911 Койка коек КОЕК 912 Тысяча коек 10³ коек ТЫС КОЕК 913 Том книжного фонда том книжн. фонд ТОМ КНИЖН ФОНД 914 Тысяча томов книжного фонда 10³ том. книжн. фонд ТЫС ТОМ КНИЖН ФОНД 915 Условный ремонт усл. рем УСЛ РЕМ 916 Условный ремонт в год усл. рем/год УСЛ РЕМ/ГОД 917 Смена смен СМЕН 918 Лист авторский л. авт ЛИСТ АВТ 920 Лист печатный л. печ ЛИСТ ПЕЧ 921 Лист учетно-издательский л. уч.-изд ЛИСТ УЧ.ИЗД 922 Знак знак ЗНАК 923 Слово слово СЛОВО 924 Символ символ СИМВОЛ 925 Условная труба усл. труб УСЛ ТРУБ 930 Тысяча пластин 10³ пласт ТЫС ПЛАСТ 937 Миллион доз 10⁶ доз МЛН ДОЗ 949 Миллион листов-оттисков 10³ лист.оттиск МЛН ЛИСТ.ОТТИСК 950 Вагоно (машино)-день ваг (маш).дн ВАГ (МАШ).ДН 951 Тысяча вагоно (машино)-часов 10³ ваг (маш).ч ТЫС ВАГ (МАШ).Ч 952 Тысяча вагоно (машино)-километров 10³ ваг (маш).км ТЫС ВАГ (МАШ).КМ 953 Тысяча место-километров 10³ мест.км ТЫС МЕСТ.КМ 954 Вагоно-сутки ваг.сут ВАГ.СУТ 955 Тысяча поездо-часов 10³ поезд.ч ТЫС ПОЕЗД.Ч 956 Тысяча поездо-километров 10³ поезд.км ТЫС ПОЕЗД.КМ 957 Тысяча тонно-миль 10³ т.миль ТЫС Т.МИЛЬ 958 Тысяча пассажиро-миль 10³ пасс.миль ТЫС ПАСС.МИЛЬ 959 Автомобиле-день автомоб.дн АВТОМОБ.ДН 960 Тысяча автомобиле-тонно-дней 10³ автомоб.т.дн ТЫС АВТОМОБ.Т.ДН 961 Тысяча автомобиле-часов 10³ автомоб.ч ТЫС АВТОМОБ.Ч 962 Тысяча автомобиле-место-дней 10³ автомоб.мест. дн ТЫС АВТОМОБ.МЕСТ. ДН 963 Приведенный час привед.ч ПРИВЕД.Ч 964 Самолето-километр самолет.км САМОЛЕТ.КМ 965 Тысяча километров 10³ км ТЫС КМ 966 Тысяча тоннаже-рейсов 10³ тоннаж. рейс ТЫС ТОННАЖ. РЕЙС 967 Миллион тонно-миль 10⁶ т. миль МЛН Т. МИЛЬ 968 Миллион пассажиро-миль 10⁶ пасс. миль МЛН ПАСС. МИЛЬ 969 Миллион тоннаже-миль 10⁶ тоннаж. миль МЛН ТОННАЖ. МИЛЬ 970 Миллион пассажиро-место-миль 10⁶ пасс. мест. миль МЛН ПАСС. МЕСТ. МИЛЬ 971 Кормо-день корм. дн КОРМ. ДН 972 Центнер кормовых единиц ц корм ед Ц КОРМ ЕД 973 Тысяча автомобиле-километров 10³ автомоб. км ТЫС АВТОМОБ. КМ 974 Тысяча тоннаже-суток 10³ тоннаж. сут ТЫС ТОННАЖ. СУТ 975 Суго-сутки суго. сут. СУГО. СУТ 976 Штук в 20-футовом эквиваленте (ДФЭ) штук в 20-футовом эквиваленте ШТ В 20 ФУТ ЭКВИВ 977 Канало-километр канал. км КАНАЛ. КМ 978 Канало-концы канал. конц КАНАЛ. КОНЦ 979 Тысяча экземпляров 10³ экз ТЫС ЭКЗ 980 Тысяча долларов 10³ доллар ТЫС ДОЛЛАР 981 Тысяча тонн кормовых единиц 10³ корм ед ТЫС Т КОРМ ЕД 982 Миллион тонн кормовых единиц 10⁶ корм ед МЛН Т КОРМ ЕД 983 Судо-сутки суд.сут СУД.СУТ 984 Центнеров с гектара 985 Тысяча голов 986 Тысяча краско-оттисков 987 Миллион краско-оттисков 988 Миллион условных плиток 989 Человек в час 990 Пассажиров в час 991 Пассажиро-миля 2541 Бит в секунду 2543 Килобит в секунду 2545 Мегабит в секунду 2547 Гигабит в секунду 2551 Байт в секунду 2552 Гигабайт в секунду 2553 Гигабайт 2554 Терабайт 2555 Петабайт 2556 Эксабайт 2557 Зеттабайт 2558 Йоттабайт 2561 Килобайт в секунду 2571 Мегабайт в секунду 2581 Эрланг 2931 Гигагерц 3135 Децибел 3181 Человеко-зиверт чел.-Зв ЧЕЛ.-ЗВ 3231 Беккерель на метр кубический Бк/м³ БК/M3 3831 Рубль тонна 5401 Дето-день 5423 Человек в год 5451 Посещение 5562 Тысяча гнезд 6421 Единиц в год 6422 Вызов 6423 Посевная единица 6424 Штамм 7923 Абонент 8361 Особь 8751 Коробка 9061 Миллион гектаров 9062 Миллиард гектаров 9111 Койко-день 9113 Пациенто-день 9245 Запись 9246 Документ 9491 Лист-оттиск 9501 Вагоно (машино)-час 9557 Миллион голов 9641 Летный час 9642 Балл 9805 Доллар за тонну 9822 Миллион долларов 10⁶ евро МЛН ЕВРО 9822 Миллион евро 10⁶ евро МЛН ЕВРО 9823 Миллиард евро 10⁹ евро МЛРД ЕВРО 9823 Миллиард долларов 10⁹ евро МЛРД ЕВРО 9910 Международная единица биологической активности 9911 Тысяча международных единиц биологической активности 9912 Миллион международных единиц биологической активности 9913 Международная единица биологической активности на грамм 9914 Тысяча международных единиц биологической активности на грамм 9915 Миллион международных единиц биологической активности на грамм 9916 Международная единица биологической активности на миллилитр 9917 Тысяча международных единиц биологической активности на миллилитр 9918 Миллион международных единиц биологической активности на миллилитр 9920 Единица действия биологической активности 9921 Единица действия биологической активности на грамм 9922 Тысяча единиц действия биологической активности на грамм 9923 Единица действия биологической активности на микролитр 9924 Единица действия биологической активности на миллилитр 9925 Тысяча единиц действия биологической активности на миллилитр 9926 Миллион единиц действия биологической активности на миллилитр 9927 Единица действия биологической активности в сутки 9930 Антитоксическая единица 9931 Тысяча антитоксических единиц 9940 Антитрипсиновая единица 9941 Тысяча антитрипсиновых единиц 9950 Индекс Реактивности 9951 Индекс Реактивности на миллилитр 9960 Килобеккерель на миллилитр 9961 Мегабеккерель на миллилитр 9962 Мегабеккерель на метр квадратный 9970 Калликреиновая ингибирующая единица на миллилитр 9971 Тысяча калликреиновых ингибирующих единиц на миллилитр 9980 Миллион колониеобразующих единиц 9981 Миллион колониеобразующих единиц на пакет 9982 Миллиард колониеобразующих единиц 9983 Протеолитическая единица 9985 Микрограмм на миллилитр 9986 Микрограмм в сутки 9987 Микрограмм в час 9988 Микрограмм на дозу 9990 Миллимоль на миллилитр 9991 Миллимоль на литр

«kg» redirects here. For other uses, see KG.

Kilogram
A Kibble balance is used to measure a kilogram with electricity and magnetism
General information
Unit system	SI
Unit of	mass
Symbol	kg
Conversions
1 kg in …	… is equal to …
Avoirdupois	≈ 2.204623 pounds[Note 1]
British Gravitational	≈ 0.0685 slugs

The kilogram (also kilogramme^[1]) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. It means ‘one thousand grams’.

The kilogram is defined in terms of the second and the metre, both of which are based on fundamental physical constants. This allows a properly equipped metrology laboratory to calibrate a mass measurement instrument such as a Kibble balance as the primary standard to determine an exact kilogram mass.^[2][3]

The kilogram was originally defined in 1795 as the mass of one litre of water. The current definition of a kilogram agrees with this original definition to within 30 parts per million. In 1799, the platinum Kilogramme des Archives replaced it as the standard of mass. In 1889, a cylinder of platinum-iridium, the International Prototype of the Kilogram (IPK), became the standard of the unit of mass for the metric system and remained so for 130 years, before the current standard was adopted in 2019.^[4]

Definition[edit]

The kilogram is defined in terms of three fundamental physical constants:

• a specific atomic transition frequency Δν_Cs, which defines the duration of the second,
• the speed of light c, which when combined with the second, defines the length of the metre,
• and the Planck constant h. which when combined with the metre and second, defines the mass of the kilogram.

The formal definition according to the General Conference on Weights and Measures (CGPM) is:

The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10⁻³⁴ when expressed in the unit J⋅s, which is equal to kg⋅m²⋅s⁻¹, where the metre and the second are defined in terms of c and Δν_Cs.

— CGPM ^[5][6]

Defined in term of those units, the kg is formulated as:^[7]

kg = (299792458)²/(6.62607015×10⁻³⁴)(9192631770)hΔν_Cs/c² = 917097121160018/6215410507259047510⁴²hΔν_Cs/c² ≈ (1.475521399735270×10⁴⁰)hΔν_Cs/c² .

This definition is generally consistent with previous definitions: the mass remains within 30 ppm of the mass of one litre of water.^[8]

Timeline of previous definitions[edit]

• 1793: The grave (the precursor of the kilogram) was defined as the mass of 1 litre (dm³) of water, which was determined to be 18841 grains.^[9]
• 1795: the gram (¹/₁₀₀₀ of a kilogram) was provisionally defined as the mass of one cubic centimetre of water at the melting point of ice.^[10]
• 1799: The Kilogramme des Archives was manufactured as a prototype. It had a mass equal to the mass of 1 dm³ of water at the temperature of its maximum density, which is approximately 4 °C.
• 1875–1889: The Metre Convention was signed in 1875, leading to the production of the International Prototype of the Kilogram (IPK) in 1879 and its adoption in 1889.
• 2019: The kilogram was defined in terms of the Planck constant, the speed of light and hyperfine transition frequency of ¹³³Cs as approved by the General Conference on Weights and Measures (CGPM) on November 16, 2018.

Name and terminology[edit]

The kilogram is the only base SI unit with an SI prefix (kilo) as part of its name. The word kilogramme or kilogram is derived from the French kilogramme,^[11] which itself was a learned coinage, prefixing the Greek stem of χίλιοι khilioi «a thousand» to gramma, a Late Latin term for «a small weight», itself from Greek γράμμα.^[12]
The word kilogramme was written into French law in 1795, in the Decree of 18 Germinal,^[13]
which revised the provisional system of units introduced by the French National Convention two years earlier, where the gravet had been defined as weight (poids) of a cubic centimetre of water, equal to 1/1000 of a grave.^[14] In the decree of 1795, the term gramme thus replaced gravet, and kilogramme replaced grave.

The French spelling was adopted in Great Britain when the word was used for the first time in English in 1795,^[15][11] with the spelling kilogram being adopted in the United States. In the United Kingdom both spellings are used, with «kilogram» having become by far the more common.^[1] UK law regulating the units to be used when trading by weight or measure does not prevent the use of either spelling.^[16]

In the 19th century the French word kilo, a shortening of kilogramme, was imported into the English language where it has been used to mean both kilogram^[17] and kilometre.^[18] While kilo as an alternative is acceptable, to The Economist for example,^[19] the Canadian government’s Termium Plus system states that «SI (International System of Units) usage, followed in scientific and technical writing» does not allow its usage and it is described as «a common informal name» on Russ Rowlett’s Dictionary of Units of Measurement.^[20][21] When the United States Congress gave the metric system legal status in 1866, it permitted the use of the word kilo as an alternative to the word kilogram,^[22] but in 1990 revoked the status of the word kilo.^[23]

The SI system was introduced in 1960 and in 1970 the BIPM started publishing the SI Brochure, which contains all relevant decisions and recommendations by the CGPM concerning units. The SI Brochure states that «It is not permissible to use abbreviations for unit symbols or unit names …».^{[24][Note 2]}

Kilogram becoming a base unit: the role of units for electromagnetism[edit]

It is primarily because of units for electromagnetism that the kilogram rather than the gram was eventually adopted as the base unit of mass in the SI. The relevant series of discussions and decisions started roughly in the 1850s and effectively concluded in 1946. By the end of the 19th century, the ‘practical units’ for electric and magnetic quantities such as the ampere and the volt were well established in practical use (e.g. for telegraphy). Unfortunately, they were not coherent with the then-prevailing base units for length and mass, the centimetre, and the gram. However, the ‘practical units’ also included some purely mechanical units. In particular, the product of the ampere and the volt gives a purely mechanical unit of power, the watt. It was noticed that the purely mechanical practical units such as the watt would be coherent in a system in which the base unit of length was the metre and the base unit of mass was the kilogram. Because no one wanted to replace the second as the base unit of time, the metre and the kilogram are the only pair of base units of length and mass such that (1) the watt is a coherent unit of power, (2) the base units of length and time are integer-power-of-ten ratios to the metre and the gram (so that the system remains ‘metric’), and (3) the sizes of the base units of length and mass are convenient for practical use.^{[Note 3]} This would still leave out the purely electrical and magnetic units: while the purely mechanical practical units such as the watt are coherent in the metre-kilogram-second system, the explicitly electrical and magnetic units such as the volt, the ampere, etc. are not.^{[Note 5]} The only way to also make those units coherent with the metre-kilogram-second system is to modify that system in a different way: the number of fundamental dimensions must be increased from three (length, mass, and time) to four (the previous three, plus one purely electrical one).^{[Note 6]}

The state of units for electromagnetism at the end of the 19th century[edit]

During the second half of the 19th century, the centimetre–gram–second system of units was becoming widely accepted for scientific work, treating the gram as the fundamental unit of mass and the kilogram as a decimal multiple of the base unit formed by using a metric prefix. However, as the century drew to a close, there was widespread dissatisfaction with the units for electricity and magnetism in the CGS system. There were two obvious choices for absolute units^{[Note 7]} of electromagnetism: the ‘electrostatic’ (CGS-ESU) system and the ‘electromagnetic’ (CGS-EMU) system. But the sizes of coherent electric and magnetic units were not convenient in either of these systems; for example, the ESU unit of electrical resistance, which was later named the statohm, corresponds to about 9×10¹¹ ohm, while the EMU unit, which was later named the abohm, corresponds to 10⁻⁹ ohm.^{[Note 8]}

To circumvent this difficulty, a third set of units was introduced: the so-called practical units. The practical units were obtained as decimal multiples of coherent CGS-EMU units, chosen so that the resulting magnitudes were convenient for practical use and so that the practical units were, as far as possible, coherent with each other.^[27] The practical units included such units as the volt, the ampere, the ohm, etc.,^[28][29] which were later incorporated in the SI system and which are used to this day.^{[Note 9]} The reason the metre and the kilogram were later chosen to be the base units of length and mass was that they are the only combination of reasonably sized decimal multiples or submultiples of the metre and the gram that can be made coherent with the volt, the ampere, etc.

The reason is that electrical quantities cannot be isolated from mechanical and thermal ones: they are connected by relations such as current × electric potential difference = power. For this reason, the practical system also included coherent units for certain mechanical quantities. For example, the previous equation implies that ampere × volt is a coherent derived practical unit of power;^{[Note 10]} this unit was named the watt. The coherent unit of energy is then the watt times the second, which was named the joule. The joule and the watt also have convenient magnitudes and are decimal multiples of CGS coherent units for energy (the erg) and power (the erg per second). The watt is not coherent in the centimetre-gram-second system, but it is coherent in the metre-kilogram-second system—and in no other system whose base units of length and mass are reasonably sized decimal multiples or submultiples of the metre and the gram.

However, unlike the watt and the joule, the explicitly electrical and magnetic units (the volt, the ampere…) are not coherent even in the (absolute three-dimensional) metre-kilogram-second system. Indeed, one can work out what the base units of length and mass have to be in order for all the practical units to be coherent (the watt and the joule as well as the volt, the ampere, etc.). The values are 10⁷ metres (one half of a meridian of the Earth, called a quadrant) and 10⁻¹¹ grams (called an eleventh-gram^{[Note 11]}).^{[Note 13]}

Therefore, the full absolute system of units in which the practical electrical units are coherent is the quadrant–eleventh-gram–second (QES) system. However, the extremely inconvenient magnitudes of the base units for length and mass made it so that no one seriously considered adopting the QES system. Thus, people working on practical applications of electricity had to use units for electrical quantities and for energy and power that were not coherent with the units they were using for e.g. length, mass, and force.

Meanwhile, scientists developed yet another fully coherent absolute system, which came to be called the Gaussian system, in which the units for purely electrical quantities are taken from CGE-ESU, while the units for magnetic quantities are taken from the CGS-EMU. This system proved very convenient for scientific work and is still widely used. However, the sizes of its units remained either too large or too small—by many orders of magnitude—for practical applications.

Finally, in both CGS-ESU and CGS-EMU as well as in the Gaussian system, Maxwell’s equations are ‘unrationalized’, meaning that they contain various factors of 4π that many workers found awkward. So yet another system was developed to rectify that: the ‘rationalized’ Gaussian system, usually called the Heaviside–Lorentz system. This system is still used in some subfields of physics. However, the units in that system are related to Gaussian units by factors of √4π ≈ 3.5, which means that their magnitudes remained, like those of the Gaussian units, either far too large or far too small for practical applications.

The Giorgi proposal[edit]

In 1901, Giovanni Giorgi proposed a new system of units that would remedy this situation.^[30] He noted that the mechanical practical units such as the joule and the watt are coherent not only in the QES system, but also in the metre-kilogram-second (MKS) system.^{[31][Note 14]} It was of course known that adopting the metre and the kilogram as base units—obtaining the three dimensional MKS system—would not solve the problem: while the watt and the joule would be coherent, this would not be so for the volt, the ampere, the ohm, and the rest of the practical units for electric and magnetic quantities (the only three-dimensional absolute system in which all practical units are coherent is the QES system).

But Giorgi pointed out that the volt and the rest could be made coherent if the idea that all physical quantities must be expressible in terms of dimensions of length, mass, and time, is relinquished and a fourth base dimension is added for electric quantities. Any practical electrical unit could be chosen as the new fundamental unit, independent from the metre, kilogram, and second. Likely candidates for the fourth independent unit included the coulomb, the ampere, the volt, and the ohm, but eventually, the ampere proved to be the most convenient for metrology. Moreover, the freedom gained by making an electric unit independent from the mechanical units could be used to rationalize Maxwell’s equations.

The idea that one should give up on having a purely ‘absolute’ system (i.e. one where only length, mass, and time are the base dimensions) was a departure from a viewpoint that seemed to underlie the early breakthroughs by Gauss and Weber (especially their famous ‘absolute measurements’ of Earth’s magnetic field^{[32]: 54–56}), and it took some time for the scientific community to accept it—not least because many scientists clung to the notion that the dimensions of a quantity in terms of length, mass, and time somehow specify its ‘fundamental physical nature’.^{[33]:24, 26[31]}

Acceptance of the Giorgi system, leading to the MKSA system and the SI[edit]

By the 1920s, dimensional analysis had become much better understood^[31] and it was becoming widely accepted that the choice of both the number and of the identities of the «fundamental» dimensions should be dictated by convenience only and that there is nothing really fundamental about the dimensions of a quantity.^[33] In 1935, Giorgi’s proposal was adopted by the IEC as the Giorgi system. It is this system that has since then been called the MKS system,^[34]
although ‘MKSA’ appears in careful usage. In 1946 the CIPM approved a proposal to adopt the ampere as the electromagnetic unit of the «MKSA system».^{[35]: 109, 110} In 1948 the CGPM commissioned the CIPM «to make recommendations for a single practical system of units of measurement, suitable for adoption by all countries adhering to the Metre Convention».^[36] This led to the launch of SI in 1960.

To summarize, the ultimate reason that the kilogram was chosen over the gram as the base unit of mass was, in one word, the volt-ampere. Namely, the combination of the metre and the kilogram was the only choice of base units of length and mass such that 1. the volt-ampere—which is also called the watt and which is the unit of power in the practical system of electrical units—is coherent, 2. the base units of length and mass are decimal multiples or submultiples of the metre and the gram, and 3. the base units of length and mass have convenient sizes.

The CGS and MKS systems co-existed during much of the early-to-mid-20th century, but as a result of the decision to adopt the «Giorgi system» as the international system of units in 1960, the kilogram is now the SI base unit for mass, while the definition of the gram is derived.

Redefinition based on fundamental constants[edit]

The replacement of the International Prototype of the Kilogram (IPK) as the primary standard was motivated by evidence accumulated over a long period of time that the mass of the IPK and its replicas had been changing; the IPK had diverged from its replicas by approximately 50 micrograms since their manufacture late in the 19th century. This led to several competing efforts to develop measurement technology precise enough to warrant replacing the kilogram artefact with a definition based directly on physical fundamental constants.^[4] Physical standard masses such as the IPK and its replicas still serve as secondary standards.

The International Committee for Weights and Measures (CIPM) approved a redefinition of the SI base units in November 2018 that defines the kilogram by defining the Planck constant to be exactly 6.62607015×10⁻³⁴ kg⋅m²⋅s⁻¹, effectively defining the kilogram in terms of the second and the metre. The new definition took effect on May 20, 2019.^[4][5][37]

Prior to the redefinition, the kilogram and several other SI units based on the kilogram were defined by a man-made metal artifact: the Kilogramme des Archives from 1799 to 1889, and the IPK from 1889 to 2019.^[4]

In 1960, the metre, previously similarly having been defined with reference to a single platinum-iridium bar with two marks on it, was redefined in terms of an invariant physical constant (the wavelength of a particular emission of light emitted by krypton,^[38] and later the speed of light) so that the standard can be independently reproduced in different laboratories by following a written specification.

At the 94th Meeting of the International Committee for Weights and Measures (CIPM) in 2005, it was recommended that the same be done with the kilogram.^[39]

In October 2010, the CIPM voted to submit a resolution for consideration at the General Conference on Weights and Measures (CGPM), to «take note of an intention» that the kilogram be defined in terms of the Planck constant, h (which has dimensions of energy times time, thus mass × length² / time) together with other physical constants.^[40][41] This resolution was accepted by the 24th conference of the CGPM^[42] in October 2011 and further discussed at the 25th conference in 2014.^[43][44] Although the Committee recognised that significant progress had been made, they concluded that the data did not yet appear sufficiently robust to adopt the revised definition, and that work should continue to enable the adoption at the 26th meeting, scheduled for 2018.^[43] Such a definition would theoretically permit any apparatus that was capable of delineating the kilogram in terms of the Planck constant to be used as long as it possessed sufficient precision, accuracy and stability. The Kibble balance is one way to do this.

As part of this project, a variety of very different technologies and approaches were considered and explored over many years. Some of these approaches were based on equipment and procedures that would enable the reproducible production of new, kilogram-mass prototypes on demand (albeit with extraordinary effort) using measurement techniques and material properties that are ultimately based on, or traceable to, physical constants. Others were based on devices that measured either the acceleration or weight of hand-tuned kilogram test masses and which expressed their magnitudes in electrical terms via special components that permit traceability to physical constants. All approaches depend on converting a weight measurement to a mass and therefore require the precise measurement of the strength of gravity in laboratories. All approaches would have precisely fixed one or more constants of nature at a defined value.

SI multiples[edit]

Because an SI unit may not have multiple prefixes (see SI prefix), prefixes are added to gram, rather than the base unit kilogram, which already has a prefix as part of its name.^[45] For instance, one-millionth of a kilogram is 1 mg (one milligram), not 1 μkg (one microkilogram).

• The microgram is typically abbreviated «mcg» in pharmaceutical and nutritional supplement labelling, to avoid confusion, since the «μ» prefix is not always well recognised outside of technical disciplines.^{[Note 16]} (The expression «mcg» is also the symbol for an obsolete CGS unit of measure known as the «millicentigram», which is equal to 10 μg.)
• In the United Kingdom, because serious medication errors have been made from the confusion between milligrams and micrograms when micrograms has been abbreviated, the recommendation given in the Scottish Palliative Care Guidelines is that doses of less than one milligram must be expressed in micrograms and that the word microgram must be written in full, and that it is never acceptable to use «mcg» or «μg».^[46]
• The hectogram (100 g) (Italian: ettogrammo or etto) is a very commonly used unit in the retail food trade in Italy.^[47][48][49]
• The former standard spelling and abbreviation «deka-» and «dk» produced abbreviations such as «dkm» (dekametre) and «dkg» (dekagram).^[50] As of 2020, the abbreviation «dkg» (10 g) is still used in parts of central Europe in retail for some foods such as cheese and meat.^{[51][52][53][55]}
• The unit name megagram is rarely used, and even then typically only in technical fields in contexts where especially rigorous consistency with the SI standard is desired. For most purposes, the name tonne is instead used. The tonne and its symbol, «t», were adopted by the CIPM in 1879. It is a non-SI unit accepted by the BIPM for use with the SI. According to the BIPM, «This unit is sometimes referred to as ‘metric ton’ in some English-speaking countries.»^[56] The unit name megatonne or megaton (Mt) is often used in general-interest literature on greenhouse gas emissions and nuclear weapons yields, whereas the equivalent unit in scientific papers on the subject is often the teragram (Tg).

See also[edit]

Notes[edit]

References[edit]

External links[edit]

NIST: K20, the US National Prototype Kilogram resting on an egg crate fluorescent light panel

BIPM: Steam cleaning a 1 kg prototype before a mass comparison

BIPM: The IPK and its six sister copies in their vault

The Age: Silicon sphere for the Avogadro Project

NPL: The NPL’s Watt Balance project

NIST: This particular Rueprecht Balance, an Austrian-made precision balance, was used by the NIST from 1945 until 1960

BIPM: The FB‑2 flexure-strip balance, the BIPM’s modern precision balance featuring a standard deviation of one ten-billionth of a kilogram (0.1 μg)

BIPM: Mettler HK1000 balance, featuring 1 μg resolution and a 4 kg maximum mass. Also used by NIST and Sandia National Laboratories’ Primary Standards Laboratory

Micro-g LaCoste: FG‑5 absolute gravimeter, (diagram), used in national laboratories to measure gravity to 2 μGal accuracy

• NIST Improves Accuracy of ‘Watt Balance’ Method for Defining the Kilogram
• The UK’s National Physical Laboratory (NPL): Are any problems caused by having the kilogram defined in terms of a physical artefact? (FAQ – Mass & Density)
• NPL: NPL Kibble balance
• Metrology in France: Watt balance
• Australian National Measurement Institute: Redefining the kilogram through the Avogadro constant
• International Bureau of Weights and Measures (BIPM): Home page
• NZZ Folio: What a kilogram really weighs
• NPL: What are the differences between mass, weight, force and load?
• BBC: Getting the measure of a kilogram
• NPR: This Kilogram Has A Weight-Loss Problem, an interview with National Institute of Standards and Technology physicist Richard Steiner
• Avogadro and molar Planck constants for the redefinition of the kilogram
• Realization of the awaited definition of the kilogram
• Sample, Ian (November 9, 2018). «In the balance: scientists vote on first change to kilogram in a century». The Guardian. Retrieved November 9, 2018.

Videos[edit]

• The BIPM – YouTube channel
• «The role of the Planck constant in physics» – presentation at 26th CGPM meeting at Versailles, France, November 2018 when voting on superseding the IPK took place on YouTube

«kg» redirects here. For other uses, see KG.

Kilogram
A Kibble balance is used to measure a kilogram with electricity and magnetism
General information
Unit system	SI
Unit of	mass
Symbol	kg
Conversions
1 kg in …	… is equal to …
Avoirdupois	≈ 2.204623 pounds[Note 1]
British Gravitational	≈ 0.0685 slugs

The kilogram (also kilogramme^[1]) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially. It means ‘one thousand grams’.

The kilogram is defined in terms of the second and the metre, both of which are based on fundamental physical constants. This allows a properly equipped metrology laboratory to calibrate a mass measurement instrument such as a Kibble balance as the primary standard to determine an exact kilogram mass.^[2][3]

The kilogram was originally defined in 1795 as the mass of one litre of water. The current definition of a kilogram agrees with this original definition to within 30 parts per million. In 1799, the platinum Kilogramme des Archives replaced it as the standard of mass. In 1889, a cylinder of platinum-iridium, the International Prototype of the Kilogram (IPK), became the standard of the unit of mass for the metric system and remained so for 130 years, before the current standard was adopted in 2019.^[4]

Definition[edit]

The kilogram is defined in terms of three fundamental physical constants:

• a specific atomic transition frequency Δν_Cs, which defines the duration of the second,
• the speed of light c, which when combined with the second, defines the length of the metre,
• and the Planck constant h. which when combined with the metre and second, defines the mass of the kilogram.

The formal definition according to the General Conference on Weights and Measures (CGPM) is:

The kilogram, symbol kg, is the SI unit of mass. It is defined by taking the fixed numerical value of the Planck constant h to be 6.62607015×10⁻³⁴ when expressed in the unit J⋅s, which is equal to kg⋅m²⋅s⁻¹, where the metre and the second are defined in terms of c and Δν_Cs.

— CGPM ^[5][6]

Defined in term of those units, the kg is formulated as:^[7]

kg = (299792458)²/(6.62607015×10⁻³⁴)(9192631770)hΔν_Cs/c² = 917097121160018/6215410507259047510⁴²hΔν_Cs/c² ≈ (1.475521399735270×10⁴⁰)hΔν_Cs/c² .

This definition is generally consistent with previous definitions: the mass remains within 30 ppm of the mass of one litre of water.^[8]

Timeline of previous definitions[edit]

• 1793: The grave (the precursor of the kilogram) was defined as the mass of 1 litre (dm³) of water, which was determined to be 18841 grains.^[9]
• 1795: the gram (¹/₁₀₀₀ of a kilogram) was provisionally defined as the mass of one cubic centimetre of water at the melting point of ice.^[10]
• 1799: The Kilogramme des Archives was manufactured as a prototype. It had a mass equal to the mass of 1 dm³ of water at the temperature of its maximum density, which is approximately 4 °C.
• 1875–1889: The Metre Convention was signed in 1875, leading to the production of the International Prototype of the Kilogram (IPK) in 1879 and its adoption in 1889.
• 2019: The kilogram was defined in terms of the Planck constant, the speed of light and hyperfine transition frequency of ¹³³Cs as approved by the General Conference on Weights and Measures (CGPM) on November 16, 2018.

Name and terminology[edit]

The kilogram is the only base SI unit with an SI prefix (kilo) as part of its name. The word kilogramme or kilogram is derived from the French kilogramme,^[11] which itself was a learned coinage, prefixing the Greek stem of χίλιοι khilioi «a thousand» to gramma, a Late Latin term for «a small weight», itself from Greek γράμμα.^[12]
The word kilogramme was written into French law in 1795, in the Decree of 18 Germinal,^[13]
which revised the provisional system of units introduced by the French National Convention two years earlier, where the gravet had been defined as weight (poids) of a cubic centimetre of water, equal to 1/1000 of a grave.^[14] In the decree of 1795, the term gramme thus replaced gravet, and kilogramme replaced grave.

The French spelling was adopted in Great Britain when the word was used for the first time in English in 1795,^[15][11] with the spelling kilogram being adopted in the United States. In the United Kingdom both spellings are used, with «kilogram» having become by far the more common.^[1] UK law regulating the units to be used when trading by weight or measure does not prevent the use of either spelling.^[16]

In the 19th century the French word kilo, a shortening of kilogramme, was imported into the English language where it has been used to mean both kilogram^[17] and kilometre.^[18] While kilo as an alternative is acceptable, to The Economist for example,^[19] the Canadian government’s Termium Plus system states that «SI (International System of Units) usage, followed in scientific and technical writing» does not allow its usage and it is described as «a common informal name» on Russ Rowlett’s Dictionary of Units of Measurement.^[20][21] When the United States Congress gave the metric system legal status in 1866, it permitted the use of the word kilo as an alternative to the word kilogram,^[22] but in 1990 revoked the status of the word kilo.^[23]

The SI system was introduced in 1960 and in 1970 the BIPM started publishing the SI Brochure, which contains all relevant decisions and recommendations by the CGPM concerning units. The SI Brochure states that «It is not permissible to use abbreviations for unit symbols or unit names …».^{[24][Note 2]}

Kilogram becoming a base unit: the role of units for electromagnetism[edit]

It is primarily because of units for electromagnetism that the kilogram rather than the gram was eventually adopted as the base unit of mass in the SI. The relevant series of discussions and decisions started roughly in the 1850s and effectively concluded in 1946. By the end of the 19th century, the ‘practical units’ for electric and magnetic quantities such as the ampere and the volt were well established in practical use (e.g. for telegraphy). Unfortunately, they were not coherent with the then-prevailing base units for length and mass, the centimetre, and the gram. However, the ‘practical units’ also included some purely mechanical units. In particular, the product of the ampere and the volt gives a purely mechanical unit of power, the watt. It was noticed that the purely mechanical practical units such as the watt would be coherent in a system in which the base unit of length was the metre and the base unit of mass was the kilogram. Because no one wanted to replace the second as the base unit of time, the metre and the kilogram are the only pair of base units of length and mass such that (1) the watt is a coherent unit of power, (2) the base units of length and time are integer-power-of-ten ratios to the metre and the gram (so that the system remains ‘metric’), and (3) the sizes of the base units of length and mass are convenient for practical use.^{[Note 3]} This would still leave out the purely electrical and magnetic units: while the purely mechanical practical units such as the watt are coherent in the metre-kilogram-second system, the explicitly electrical and magnetic units such as the volt, the ampere, etc. are not.^{[Note 5]} The only way to also make those units coherent with the metre-kilogram-second system is to modify that system in a different way: the number of fundamental dimensions must be increased from three (length, mass, and time) to four (the previous three, plus one purely electrical one).^{[Note 6]}

The state of units for electromagnetism at the end of the 19th century[edit]

During the second half of the 19th century, the centimetre–gram–second system of units was becoming widely accepted for scientific work, treating the gram as the fundamental unit of mass and the kilogram as a decimal multiple of the base unit formed by using a metric prefix. However, as the century drew to a close, there was widespread dissatisfaction with the units for electricity and magnetism in the CGS system. There were two obvious choices for absolute units^{[Note 7]} of electromagnetism: the ‘electrostatic’ (CGS-ESU) system and the ‘electromagnetic’ (CGS-EMU) system. But the sizes of coherent electric and magnetic units were not convenient in either of these systems; for example, the ESU unit of electrical resistance, which was later named the statohm, corresponds to about 9×10¹¹ ohm, while the EMU unit, which was later named the abohm, corresponds to 10⁻⁹ ohm.^{[Note 8]}

To circumvent this difficulty, a third set of units was introduced: the so-called practical units. The practical units were obtained as decimal multiples of coherent CGS-EMU units, chosen so that the resulting magnitudes were convenient for practical use and so that the practical units were, as far as possible, coherent with each other.^[27] The practical units included such units as the volt, the ampere, the ohm, etc.,^[28][29] which were later incorporated in the SI system and which are used to this day.^{[Note 9]} The reason the metre and the kilogram were later chosen to be the base units of length and mass was that they are the only combination of reasonably sized decimal multiples or submultiples of the metre and the gram that can be made coherent with the volt, the ampere, etc.

The reason is that electrical quantities cannot be isolated from mechanical and thermal ones: they are connected by relations such as current × electric potential difference = power. For this reason, the practical system also included coherent units for certain mechanical quantities. For example, the previous equation implies that ampere × volt is a coherent derived practical unit of power;^{[Note 10]} this unit was named the watt. The coherent unit of energy is then the watt times the second, which was named the joule. The joule and the watt also have convenient magnitudes and are decimal multiples of CGS coherent units for energy (the erg) and power (the erg per second). The watt is not coherent in the centimetre-gram-second system, but it is coherent in the metre-kilogram-second system—and in no other system whose base units of length and mass are reasonably sized decimal multiples or submultiples of the metre and the gram.

However, unlike the watt and the joule, the explicitly electrical and magnetic units (the volt, the ampere…) are not coherent even in the (absolute three-dimensional) metre-kilogram-second system. Indeed, one can work out what the base units of length and mass have to be in order for all the practical units to be coherent (the watt and the joule as well as the volt, the ampere, etc.). The values are 10⁷ metres (one half of a meridian of the Earth, called a quadrant) and 10⁻¹¹ grams (called an eleventh-gram^{[Note 11]}).^{[Note 13]}

Therefore, the full absolute system of units in which the practical electrical units are coherent is the quadrant–eleventh-gram–second (QES) system. However, the extremely inconvenient magnitudes of the base units for length and mass made it so that no one seriously considered adopting the QES system. Thus, people working on practical applications of electricity had to use units for electrical quantities and for energy and power that were not coherent with the units they were using for e.g. length, mass, and force.

Meanwhile, scientists developed yet another fully coherent absolute system, which came to be called the Gaussian system, in which the units for purely electrical quantities are taken from CGE-ESU, while the units for magnetic quantities are taken from the CGS-EMU. This system proved very convenient for scientific work and is still widely used. However, the sizes of its units remained either too large or too small—by many orders of magnitude—for practical applications.

Finally, in both CGS-ESU and CGS-EMU as well as in the Gaussian system, Maxwell’s equations are ‘unrationalized’, meaning that they contain various factors of 4π that many workers found awkward. So yet another system was developed to rectify that: the ‘rationalized’ Gaussian system, usually called the Heaviside–Lorentz system. This system is still used in some subfields of physics. However, the units in that system are related to Gaussian units by factors of √4π ≈ 3.5, which means that their magnitudes remained, like those of the Gaussian units, either far too large or far too small for practical applications.

The Giorgi proposal[edit]

In 1901, Giovanni Giorgi proposed a new system of units that would remedy this situation.^[30] He noted that the mechanical practical units such as the joule and the watt are coherent not only in the QES system, but also in the metre-kilogram-second (MKS) system.^{[31][Note 14]} It was of course known that adopting the metre and the kilogram as base units—obtaining the three dimensional MKS system—would not solve the problem: while the watt and the joule would be coherent, this would not be so for the volt, the ampere, the ohm, and the rest of the practical units for electric and magnetic quantities (the only three-dimensional absolute system in which all practical units are coherent is the QES system).

But Giorgi pointed out that the volt and the rest could be made coherent if the idea that all physical quantities must be expressible in terms of dimensions of length, mass, and time, is relinquished and a fourth base dimension is added for electric quantities. Any practical electrical unit could be chosen as the new fundamental unit, independent from the metre, kilogram, and second. Likely candidates for the fourth independent unit included the coulomb, the ampere, the volt, and the ohm, but eventually, the ampere proved to be the most convenient for metrology. Moreover, the freedom gained by making an electric unit independent from the mechanical units could be used to rationalize Maxwell’s equations.

The idea that one should give up on having a purely ‘absolute’ system (i.e. one where only length, mass, and time are the base dimensions) was a departure from a viewpoint that seemed to underlie the early breakthroughs by Gauss and Weber (especially their famous ‘absolute measurements’ of Earth’s magnetic field^{[32]: 54–56}), and it took some time for the scientific community to accept it—not least because many scientists clung to the notion that the dimensions of a quantity in terms of length, mass, and time somehow specify its ‘fundamental physical nature’.^{[33]:24, 26[31]}

Acceptance of the Giorgi system, leading to the MKSA system and the SI[edit]

By the 1920s, dimensional analysis had become much better understood^[31] and it was becoming widely accepted that the choice of both the number and of the identities of the «fundamental» dimensions should be dictated by convenience only and that there is nothing really fundamental about the dimensions of a quantity.^[33] In 1935, Giorgi’s proposal was adopted by the IEC as the Giorgi system. It is this system that has since then been called the MKS system,^[34]
although ‘MKSA’ appears in careful usage. In 1946 the CIPM approved a proposal to adopt the ampere as the electromagnetic unit of the «MKSA system».^{[35]: 109, 110} In 1948 the CGPM commissioned the CIPM «to make recommendations for a single practical system of units of measurement, suitable for adoption by all countries adhering to the Metre Convention».^[36] This led to the launch of SI in 1960.

To summarize, the ultimate reason that the kilogram was chosen over the gram as the base unit of mass was, in one word, the volt-ampere. Namely, the combination of the metre and the kilogram was the only choice of base units of length and mass such that 1. the volt-ampere—which is also called the watt and which is the unit of power in the practical system of electrical units—is coherent, 2. the base units of length and mass are decimal multiples or submultiples of the metre and the gram, and 3. the base units of length and mass have convenient sizes.

The CGS and MKS systems co-existed during much of the early-to-mid-20th century, but as a result of the decision to adopt the «Giorgi system» as the international system of units in 1960, the kilogram is now the SI base unit for mass, while the definition of the gram is derived.

Redefinition based on fundamental constants[edit]

The replacement of the International Prototype of the Kilogram (IPK) as the primary standard was motivated by evidence accumulated over a long period of time that the mass of the IPK and its replicas had been changing; the IPK had diverged from its replicas by approximately 50 micrograms since their manufacture late in the 19th century. This led to several competing efforts to develop measurement technology precise enough to warrant replacing the kilogram artefact with a definition based directly on physical fundamental constants.^[4] Physical standard masses such as the IPK and its replicas still serve as secondary standards.

The International Committee for Weights and Measures (CIPM) approved a redefinition of the SI base units in November 2018 that defines the kilogram by defining the Planck constant to be exactly 6.62607015×10⁻³⁴ kg⋅m²⋅s⁻¹, effectively defining the kilogram in terms of the second and the metre. The new definition took effect on May 20, 2019.^[4][5][37]

Prior to the redefinition, the kilogram and several other SI units based on the kilogram were defined by a man-made metal artifact: the Kilogramme des Archives from 1799 to 1889, and the IPK from 1889 to 2019.^[4]

In 1960, the metre, previously similarly having been defined with reference to a single platinum-iridium bar with two marks on it, was redefined in terms of an invariant physical constant (the wavelength of a particular emission of light emitted by krypton,^[38] and later the speed of light) so that the standard can be independently reproduced in different laboratories by following a written specification.

At the 94th Meeting of the International Committee for Weights and Measures (CIPM) in 2005, it was recommended that the same be done with the kilogram.^[39]

In October 2010, the CIPM voted to submit a resolution for consideration at the General Conference on Weights and Measures (CGPM), to «take note of an intention» that the kilogram be defined in terms of the Planck constant, h (which has dimensions of energy times time, thus mass × length² / time) together with other physical constants.^[40][41] This resolution was accepted by the 24th conference of the CGPM^[42] in October 2011 and further discussed at the 25th conference in 2014.^[43][44] Although the Committee recognised that significant progress had been made, they concluded that the data did not yet appear sufficiently robust to adopt the revised definition, and that work should continue to enable the adoption at the 26th meeting, scheduled for 2018.^[43] Such a definition would theoretically permit any apparatus that was capable of delineating the kilogram in terms of the Planck constant to be used as long as it possessed sufficient precision, accuracy and stability. The Kibble balance is one way to do this.

As part of this project, a variety of very different technologies and approaches were considered and explored over many years. Some of these approaches were based on equipment and procedures that would enable the reproducible production of new, kilogram-mass prototypes on demand (albeit with extraordinary effort) using measurement techniques and material properties that are ultimately based on, or traceable to, physical constants. Others were based on devices that measured either the acceleration or weight of hand-tuned kilogram test masses and which expressed their magnitudes in electrical terms via special components that permit traceability to physical constants. All approaches depend on converting a weight measurement to a mass and therefore require the precise measurement of the strength of gravity in laboratories. All approaches would have precisely fixed one or more constants of nature at a defined value.

SI multiples[edit]

Because an SI unit may not have multiple prefixes (see SI prefix), prefixes are added to gram, rather than the base unit kilogram, which already has a prefix as part of its name.^[45] For instance, one-millionth of a kilogram is 1 mg (one milligram), not 1 μkg (one microkilogram).

• The microgram is typically abbreviated «mcg» in pharmaceutical and nutritional supplement labelling, to avoid confusion, since the «μ» prefix is not always well recognised outside of technical disciplines.^{[Note 16]} (The expression «mcg» is also the symbol for an obsolete CGS unit of measure known as the «millicentigram», which is equal to 10 μg.)
• In the United Kingdom, because serious medication errors have been made from the confusion between milligrams and micrograms when micrograms has been abbreviated, the recommendation given in the Scottish Palliative Care Guidelines is that doses of less than one milligram must be expressed in micrograms and that the word microgram must be written in full, and that it is never acceptable to use «mcg» or «μg».^[46]
• The hectogram (100 g) (Italian: ettogrammo or etto) is a very commonly used unit in the retail food trade in Italy.^[47][48][49]
• The former standard spelling and abbreviation «deka-» and «dk» produced abbreviations such as «dkm» (dekametre) and «dkg» (dekagram).^[50] As of 2020, the abbreviation «dkg» (10 g) is still used in parts of central Europe in retail for some foods such as cheese and meat.^{[51][52][53][55]}
• The unit name megagram is rarely used, and even then typically only in technical fields in contexts where especially rigorous consistency with the SI standard is desired. For most purposes, the name tonne is instead used. The tonne and its symbol, «t», were adopted by the CIPM in 1879. It is a non-SI unit accepted by the BIPM for use with the SI. According to the BIPM, «This unit is sometimes referred to as ‘metric ton’ in some English-speaking countries.»^[56] The unit name megatonne or megaton (Mt) is often used in general-interest literature on greenhouse gas emissions and nuclear weapons yields, whereas the equivalent unit in scientific papers on the subject is often the teragram (Tg).

See also[edit]

Notes[edit]

References[edit]

External links[edit]

NIST: K20, the US National Prototype Kilogram resting on an egg crate fluorescent light panel

BIPM: Steam cleaning a 1 kg prototype before a mass comparison

BIPM: The IPK and its six sister copies in their vault

The Age: Silicon sphere for the Avogadro Project

NPL: The NPL’s Watt Balance project

NIST: This particular Rueprecht Balance, an Austrian-made precision balance, was used by the NIST from 1945 until 1960

BIPM: The FB‑2 flexure-strip balance, the BIPM’s modern precision balance featuring a standard deviation of one ten-billionth of a kilogram (0.1 μg)

BIPM: Mettler HK1000 balance, featuring 1 μg resolution and a 4 kg maximum mass. Also used by NIST and Sandia National Laboratories’ Primary Standards Laboratory

Micro-g LaCoste: FG‑5 absolute gravimeter, (diagram), used in national laboratories to measure gravity to 2 μGal accuracy

• NIST Improves Accuracy of ‘Watt Balance’ Method for Defining the Kilogram
• The UK’s National Physical Laboratory (NPL): Are any problems caused by having the kilogram defined in terms of a physical artefact? (FAQ – Mass & Density)
• NPL: NPL Kibble balance
• Metrology in France: Watt balance
• Australian National Measurement Institute: Redefining the kilogram through the Avogadro constant
• International Bureau of Weights and Measures (BIPM): Home page
• NZZ Folio: What a kilogram really weighs
• NPL: What are the differences between mass, weight, force and load?
• BBC: Getting the measure of a kilogram
• NPR: This Kilogram Has A Weight-Loss Problem, an interview with National Institute of Standards and Technology physicist Richard Steiner
• Avogadro and molar Planck constants for the redefinition of the kilogram
• Realization of the awaited definition of the kilogram
• Sample, Ian (November 9, 2018). «In the balance: scientists vote on first change to kilogram in a century». The Guardian. Retrieved November 9, 2018.

Videos[edit]

• The BIPM – YouTube channel
• «The role of the Planck constant in physics» – presentation at 26th CGPM meeting at Versailles, France, November 2018 when voting on superseding the IPK took place on YouTube

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