international system units international system units french international modern form metric system widely system measurement comprises coherent system units measurement built seven base units defines named units includes unnamed coherent derived units system establishes set unit names unit symbols units system published result initiative began based metre kilogram second system units variant second system intended evolving system units created unit definitions modified international agreement technology measurement progresses precision measurements improves 24th 25th example discussed proposal change definition kilogram linking nature mass material ensuring long term stability motivation development diversity units sprung systems lack coordination disciplines established brought international organisations agree definitions standards new system agree rules writing presenting measurements manner world adopted developed countries adoption universal english speaking countries united_states consistent science medicine government fields technology engineering common measurements performed united_states customary units officially defined terms units united_kingdom officially adopted policy partial canada adopted governmental medical scientific purposes varied uses grocery weights weather reports traffic signs gasoline sales imperial units legally permitted remain common use sectors canadian society particularly building trade railway sector history metric system implemented french revolution metre kilogram standards length mass respectively 1830s laid foundations coherent system based length mass time 1860s group working auspices formulated requirement coherent system units base units derived units inclusion electrical units system hampered customary use set units identified need define single electrical quantity fourth base quantity alongside original base quantities treaty metre passed responsibility kilogram metre agreed prototypes french international control treaty extended include physical quantities including electrical units originally defined overhaul metric system set motion resulted development practical system units publication given international system units 10th general conference weights measures identified electric current fourth base quantity practical system units added base quantities temperature intensity making base quantities units associated quantities metre kilogram second seventh base quantity substance represented mole added definition early development metric system developed onwards committee commissioned create unified rational system measures group included father modern chemistry principles relating length volume mass proposed english clergyman concept earth basis definition length originally proposed french abbot march assembly adopted committee proposed principles new system measure authorised survey barcelona establish length july committee proposed names metre grave units length area capacity mass respectively committee proposed units denoted based thousand law april defined terms replaced terms correctly grave june completed survey definitive standard des archives des archives deposited archives december month napoleon coup état law metric system definitively adopted france passed half nineteenth century little consistency choice preferred base units typically metres widespread use france parts germany kilogram grams mass german mathematician assisted defined second base unit quoted earth magnetic field terms millimetres grams seconds prior strength earth magnetic field described relative terms technique induced suspended known mass earth magnetic field induced equivalent system gravity resultant calculations enabled assign dimensions based mass length time magnetic field 1860s later lord working auspices built work concept coherent system units base units derived units principle successfully define number units measure based second system units including energy force pressure dynamic metre convention french inspired initiative international cooperation led signing initially convention covered standards metre kilogram set prototypes metre prototypes kilogram case manufactured british firm accepted selected random international prototype metre international prototype kilogram replaced des archives des archives respectively member state entitled remaining prototypes serve national prototype country treaty established international organisations oversee keeping international standards measurement general conference weights measures des meeting years delegates member states receives discusses report new developments advice international des committee meets annually eighteen individuals high scientific standing nominated advise administrative technical matters international des international centre france custody international prototype kilogram provides services houses organisations hosts formal meetings initially prime purpose periodic national prototype metres kilograms international prototype extended include physical units including defined fourth international conference chicago enabling address inconsistencies way metric system official language french definitive version official documents published behalf french language version close 19th century different systems units measure existed electrical measurements based system units known system based system units based system international system electrical distribution systems attempts resolve electrical units terms length mass time dimensional analysis difficulties dimensions depended systems resolved published paper advocated fourth base unit alongside existing base units fourth unit chosen electric current voltage electrical resistance late 19th early 20th centuries number non coherent units measure based kilogram metre second metric horsepower power use millimetres mercury measurement barometric blood pressure developed propagated incorporated standard gravity definitions end second world war number different systems measurement use world systems metric system variations based customary systems measure representations 9th general conference weights measures asked conduct international study measurement needs scientific technical educational communities recommendations single practical system units measurement suitable adoption countries metre convention basis findings study 10th decided international system derived base units provide measurement temperature optical radiation addition mechanical electromagnetic quantities base units recommended metre kilogram second degree later renamed 11th named system abbreviated french international described modern metric system seventh base unit mole added 14th system based seven base quantities length mass time electric current temperature substance intensity quantities area pressure electrical resistance derived base quantities clear non contradictory defines quantities measured units defined international standard finalised publication conversion factors publishes defines presents official version french line leaves scope local interpretation particularly names terms different languages example produced version document local interpretation english language publications use american english document gives general guidance use united_states conversion factors customary units writing maintenance carried committees chairman committee committee includes representatives international bodies nominees committee provides forum bodies concerned provide input respect ongoing enhancements definitions terms quantity unit dimension etc given international vocabulary publication produced working group consisting international standards organisations director quantities define units referred set international standard quantities units units consists set base units set derived units special names set based term units covers categories term coherent units includes base units coherent derived units base units base units building blocks system units derived introduced concept coherent system identified quantities base units mass length time later identified need electrical base unit theoretically electric current potential difference electrical resistance electrical charge number quantities provided base unit remaining units defined laws physics event unit electric current chosen base units temperature substance intensity added later derived units derived units formed powers products base units unlimited number derived units associated derived quantities example velocity quantity derived base quantities time length derived unit metres second symbol dimensions derived units expressed terms dimensions base units coherent units derived units contain numerical factor quantities standard gravity density water absent definitions example newton force required accelerate mass kilogram metre second squared units mass acceleration respectively units force formed newton coherent set units constant sake convenience derived units special names symbols units combination names symbols base units derived units express units derived quantities example unit force newton unit pressure defined square metre added unit names produce multiple sub original unit powers powers thousand example denotes multiple thousand denotes multiple thousand millimetres metre thousand metres kilometre combined example metre kilogram named base unit kilogram units accepted use theory physical measurement recognised units appear scientific technical commercial literature continue years come addition certain units deeply embedded history culture human race continue future units published use consistent world units grouped follows units accepted use certain units time angle legacy metric units long history consistent use mankind day non subdivisions basis time unlike foot pound regardless measured revolution mathematical advantages navigation time units navigation large degree consistency world adopted retained units alongside units having given unique symbols units minute hour day degree arc minute arc second arc astronomical unit units values units obtained table use units measure based natural phenomena particularly quantities associated phenomena orders magnitude greater equivalent unit common ones consistent symbols accepted values physical values need unified atomic mass unit constant electron mass units table number units formally sanctioned continued globe spheres including health care navigation units measure tables ensure consistent usage recommendation authors use define bar millimetre mercury nautical mile barn knot units associated system units table manual number legacy units measure specific fields found literature particularly classical certain advantages units gal writing unit symbols values quantities writing metric quantities published recommendations writing symbols length area volume mass outside domain publish recommendations quantities beginning symbol started use symbols decade revision formally adopted proposal recommended symbol universally prefix ninth approved formal recommendation writing symbols metric system basis rules known laid rules subsequently extended cover unit symbols names prefix symbols names quantity symbols written values quantities expressed published rules presentation units generally compatible published august process merging standards quantities units single set compatible documents identified standard rules covering printing quantities units unit names names units follow rules associated common english french start letter newton symbol unit begins capital letter applies degrees degree unit german names units german start capital letters spelling unit names matter guardians language concerned official british american certain units differ british english australian canadian new_zealand english uses spelling metre american english uses spelling meter respectively likewise forms units follow grammar language concerned english normal rules english grammar henry units irregular remain singular form english unit names combined denote units concerned separated space newton metre newton metre formed converting unit form newton metres unit names english space recommended number unit symbol sphere normal rules english apply unit names incorporated sense kilogram sphere chinese japanese chinese uses traditional writing unit names japanese unit names written script cases symbols written internationally recognised latin greek characters chinese basic chinese units metre second include include combined form characters 19th century compound characters similar japanese imported formed principles generally today occasionally found older technical writing units different names taiwan meter centimeter kilogram prefix means universal commonly use limited japanese set characters representing metric units created japan late 19th century characters chinese exist base units metre combined set prefix characters form additional single character units seven length units kilometre millimetre example characters common use today instead units written japanese foreign kilometre written standard kilometre sino japanese words units remain use japanese significantly square metre borrowed characters examples rare phenomenon single character loan words foreign word represented single japanese character form words similar characters coined units british units fallen use single character metric units single character units list unit symbols values quantities writing unit names language specific writing unit symbols values quantities consistent languages specific rules respect writing produced language specific areas respect american english left open identical general rules general rules writing units quantities apply text produced automated process value quantity written number followed space representing sign unit symbol rule explicitly includes percent sign symbol degrees temperature exceptions symbols plane angular degrees minutes seconds placed immediately number intervening space symbols mathematical entities period stop rules grammar demand reason denoting end sentence prefix unit symbol unit symbol compound allowed symbols derived units formed joined centre dot non breaking space symbols derived units formed division joined given negative metre second written acceptable ambiguous unacceptable letter symbols units derived person written upper case written lower case unit pressure named symbol written symbol mole written symbol measure magnetic field strength symbol measure mass exceptionally written decision prompted similarity letter especially certain english style american recommends united_states symbols units form quantities represent different quantities typical power requirement hearing aid typical power requirement suburban train 10th resolution declared symbol marker shall point line line practice point english speaking countries asia latin_america continental european languages spaces thousands contrast periods reduce confusion resulting variation forms different countries line break inside number inside compound unit number unit avoided possible line breaks coincide thousands value billion vary language language terms parts billion parts avoided alternative suggested printing symbols rules specified respect production text printing presses word like symbols written upright roman type metres seconds differentiate type quantities mass displacement consensus international standards bodies rule applied independent font surrounding text chinese japanese korean language computing commonly units prefix unit combinations unit combinations allocated single characters taking square includes letter like symbols sub ranges compatibility necessarily recommending future usage summarised symbols letter like symbol number countries addition china japan symbol currently recommended standards body print space thousands commonly called thin space typically narrower words units carefully distinguish definition unit definition base unit drawn unique provides sound theoretical basis accurate measurements definition unit procedure definition establish value associated uncertainty quantity kind unit description base units given electronic appendix published way base unit determined states method consistent laws physics realise unit current exercise overhaul definitions base units committees required shall developed determining value unit particular separate experiments carried yielding values having relative standard uncertainty determination kilogram values better balance project included experiments differences reconciled determined relative uncertainty constant derived fundamentally different methods acoustic gas constant gas better values measurements changes metre convention read international precision standards weight measure resolved conclude convention changing technology led evolution definitions standards followed principal strands changes use units measure worldwide basis changes number changes include 13th renamed degree symbol symbol 14th added mole symbol list base units 14th added symbol pressure symbol electrical list named derived units 15th added symbol activity referred gray symbol radiation list named derived units order distinguish absorbed dose dose equivalent 16th added symbol list named derived units unit dose equivalent 16th clarified break convention letter letter symbol 21st added symbol activity list named derived units original form defined values ranging symbol having value symbol having value list extended 12th 15th 19th current range addition advantage taken developments technology base units enabling use higher precision techniques retention units theory physical measurement recognised units appear scientific technical commercial literature continue years come addition certain units deeply embedded history culture human race continue future units included consistently group comprises units time angles certain legacy metric units mankind day subdivisions basis time result second minute hour day unlike foot pound regardless measured second unit units measure alongside measurement angles likewise long history consistent use revolution mathematical navigation retention degree minute second arc adopted retained units alongside units having given unique symbols use units measure based natural phenomena speed light mass approximately charge electron like consistent symbols physical values need measured interests health related units measure nuclear industry 12th accepted continued use symbol unit activity gray adopted later years similarly millimetre mercury symbol retained measuring blood pressure global adoption world widely system measurement everyday commerce science change little effect everyday life countries metric system metre kilogram second remained unchanged way changes affected measurements workplace role recommending changes formal role enforcement changes inter governmental organisation provides forum national standards legislation respect degree rate adoption varied country country countries adopted metric system subsequently adopted directly programs migrated system units world largest economy united_states followed united_kingdom west_germany france japan china india united_states united_kingdom non metric france germany metric system century china metric system years india japan adopted metric system preceding years non metric countries united_kingdom united_states considerable influence differences brought examples united_kingdom british_empire use metric units trade signed defined yard pound terms metre kilogram continued use imperial system measure export imperial system units empire system set ireland left commonwealth south_africa continued close economic ties commonwealth standard published major commonwealth country adopted metric system india reading bill metric system compulsory passed reading house_of_commons votes bill failed statute book lack parliamentary time similar false starts informed members favoured adoption metric system rationale request british exports countries metric system considering changing metric system behalf government agreed support year programme government agreed voluntary policy requiring minimal legislation costs borne fell outset rest commonwealth south_africa ireland followed years countries south_africa australia mandatory voluntary apart united_kingdom canada ireland effectively completed programs united_kingdom breakdown voluntary mid-1970s coincided united_kingdom obligations adopt metric system resulting legislation force certain areas movement adopting anti stance united_kingdom seeking number relevant consumer goods completed aspects british life especially government commerce industry imperial units widely encountered areas press everyday speech units approved use alongside areas units measure regulated high profile exceptions include sale draught beer sale milk containers united_kingdom road signs irish road signs road distances speeds converted metric units decade 21st century situation ireland similar united_kingdom canada adopted purposes imperial units legally permitted remain common use sectors canadian society particularly buildings trades railways sectors european_union largest nations established history metric system members order units measure programme facilitate trade member states issued directive directive units measure economic public health public safety administrative purposes provided instructions transition existing units measure use directive replicated recommendations addition pre additions use recommended ratified directive units measure status reviewed end mainly coherent units measure units measure phased end including use obsolete names sale timber use units force pressure use acceleration gravity use non coherent units power use measure energy measure directive silent respect units specific countries including pond dutch german french synonyms effectively prohibiting use directive revisited older units reviewed millimetre mercury blood pressure retained phased broadly units directive overhauled accommodate british irish interests retaining imperial system certain circumstances reissued directive subsequent revisions directive reflected changes definition directive use units permitted period years cut date use units extended number times extended indefinitely india india countries start programme advent independent imperial native units measure use programme started passing standards weights measures act act fixed value legacy unit mass exactly act declared non metric units measure illegal years announced programme published result initial programme conversion system units subsequent adoption years later country use imperial units originally planned replace units measure metric units new weights measures act replaced act things required weighing devices approved released market place reported traditional units encountered small manufacturing establishments marketplace alongside imperial measures particularly poorer areas use indian numbering system map system widespread found alongside place western numbering system united_states congress set framework use metric system nineteenth century united_states continues use customary units based english measure passed parliament reign purposes apart science medicine puerto_rico metric units widely vast majority population having spanish heritage february issued statement use obvious detrimental effect congress authorised emphasis examine feasibility adopting volume delivered study recommended united_states adopt units congress passed metric conversion act established national policy coordinating planning increased use metric measurement system united_states voluntary coordinated efforts ford carter force seized newspaper public response included resistance ridicule underlying reasons response include relative weights measures notably liquid measure differed measure adopted british_empire inherited united_kingdom economy influence business groups congress caused country look short term costs associated change particularly borne consumer long term benefits efficiency international trade disbanded president ronald_reagan direction removed international trade barriers amended metric conversion act designating metric system preferred system weights measures united_states trade commerce legislation stated federal government responsibility assist industry especially small business voluntarily converts metric system measurement exceptions highway construction industries planned require metric units plan cancelled highway bill military uses metric system widely partly need work armed services nations overall responsibility requirements consumer goods lies congress covered federal law details requirements certain controlled state law authorities federal originally passed amended require consumer goods directly jurisdiction labelled customary metric units industries engaged efforts amend law allow manufacturers use metric developed labeling regulations provides standard approach sections packaging law state control acceptance varies state state fourteen states accept merely citing legislation decade 21st century directive required dual unit goods sold cease end backed requests nations including japan new_zealand permit metric aid trade countries opinion united_states split bill permit metric federal level introduced significant opposition representing delayed introduction bill routine review directive postponed sunset clause dual units indefinitely amended permit metric automatically law states accept january states permit metric legislation february use metric units united_states follow pattern dual unit consumer goods mandatory consumer goods soft drinks sold metric quantities milk sold customary units engineering industry equally split automotive industry largely metric aircraft boeing designed customary units units metre kilogram remained base unit relied specific physical artifact international prototype kilogram definition unit subject periodic comparisons national standard kilograms clear divergence prototype kilograms observed 23rd meeting held recommended continue investigate methods provide exact fixed values physical nature definitions units measure place enabling transition explicit unit definitions explicit constant definitions meeting held reading united_kingdom september resolution draft changes presented meeting october agreed principle proposals forward addition speed light nature constant elementary charge constant number defined exact values international prototype kilogram retired current definitions kilogram mole revised wording definitions base units changed reflect change emphasis explicit unit explicit constant definitions meeting october reviewed progress establishing fixed values found conditions set 23rd meeting fully met reason propose revision present time 24th meeting held october sponsored resolution definition changes agreed principle conditions required met implemented november conditions set 23rd meeting unit met 25th meeting held november adopted similar resolution encouraging work establishing fixed values fundamental expected adopted 26th fall task group fundamental announced special submission data values announced event
International System of Units