Metric prefix

Ametric prefixis aunit prefixthat precedes a basic unit of measure to indicate amultiple or submultipleof the unit. All metric prefixes used today aredecadic.Each prefix has a unique symbol that is prepended to any unit symbol. The prefixkilo-,for example, may be added togramto indicatemultiplicationby one thousand: onekilogramis equal to one thousand grams. The prefixmilli-,likewise, may be added tometreto indicatedivisionby one thousand; one millimetre is equal to one thousandth of a metre.

Decimal multiplicative prefixes have been a feature of all forms of themetric system,with six of these dating back to the system's introduction in the 1790s. Metric prefixes have also been used with some non-metric units. TheSI prefixesare metric prefixes that were standardised for use in theInternational System of Units(SI) by theInternational Bureau of Weights and Measures(BIPM) in resolutions dating from 1960 to 2022.^[1]^[2]Since 2009, they have formed part of theISO/IEC 80000standard. They are also used in theUnified Code for Units of Measure(UCUM).

List of SI prefixes

The BIPM specifies twenty-fourprefixes for the International System of Units (SI).

SI prefixes
v
t
e
Prefix		Base 10	Decimal	Adoption ^{[nb 1]}
Name	Symbol	Base 10	Decimal	Adoption ^{[nb 1]}
quetta	Q	10³⁰	1000000000000000000000000000000	2022^[3]
ronna	R	10²⁷	1000000000000000000000000000	2022^[3]
yotta	Y	10²⁴	1000000000000000000000000	1991
zetta	Z	10²¹	1000000000000000000000	1991
exa	E	10¹⁸	1000000000000000000	1975^[4]
peta	P	10¹⁵	1000000000000000	1975^[4]
tera	T	10¹²	1000000000000	1960
giga	G	10⁹	1000000000	1960
mega	M	10⁶	1000000	1873
kilo	k	10³	1000	1795
hecto	h	10²	100
deca	da	10¹	10
—	—	10⁰	1	—
deci	d	10⁻¹	0.1	1795
centi	c	10⁻²	0.01
milli	m	10⁻³	0.001
micro	μ	10⁻⁶	0.000001	1873
nano	n	10⁻⁹	0.000000001	1960
pico	p	10⁻¹²	0.000000000001	1960
femto	f	10⁻¹⁵	0.000000000000001	1964
atto	a	10⁻¹⁸	0.000000000000000001	1964
zepto	z	10⁻²¹	0.000000000000000000001	1991
yocto	y	10⁻²⁴	0.000000000000000000000001	1991
ronto	r	10⁻²⁷	0.000000000000000000000000001	2022^[3]
quecto	q	10⁻³⁰	0.000000000000000000000000000001	2022^[3]
Notes ^Prefixes adopted before 1960 already existed before SI. The introduction of theCGS systemwas in 1873.

The first uses of prefixes in SI date back to the definition of kilogram after the French Revolution at the end of the 18th century. Several more prefixes came into use, and were recognised by the 1947IUPAC14th International Conference of Chemistry^[5]before being officially adopted for the first time in 1960.^[6]

The most recent prefixes adopted wereronna-,quetta-,ronto-,andquecto-in 2022, after a proposal from British metrologist Richard J. C. Brown. The large prefixesronna-andquetta-were adopted in anticipation of needs for use in data science, and because unofficial prefixes that did not meet SI requirements were already circulating. The small prefixes were also added, even without such a driver, in order to maintain symmetry.^[7]

Rules

The symbols for the units of measure are combined with the symbols for each prefix name. The SI symbols for kilometre, kilogram, and kilowatt, for instance, are km, kg, and kW, respectively. (The symbol for kilo- is k.) Except for the early prefixes ofkilo-,hecto-,anddeca-,the symbols for the prefixes for multiples are uppercase letters, and those for the prefixes for submultiples are lowercase letters.^[8]
All of the metric prefix symbols are made from upper- and lower-caseLatin lettersexcept for the symbol formicro,which is uniquely a Greek letter" $μ$ ".
Like the numbers they combine with, SI units and unit symbols are never shown initalics.The prefixes and their symbols are always prefixed to the symbol for the unit without any intervening space or punctuation.^[9]This distinguishes a prefixed unit symbol from the product of unit symbols, for which a space or mid-height dot as separator is required. So, for instance, while 'ms' means millisecond, 'm s' or 'm·s' means metre second.
Prefixes corresponding to an integer power of one thousand are generally preferred; the prefixes corresponding to tens (deci-, deca-) and hundreds (centi-, hecto-) are less common and are disfavoured in certain fields. Hence, 100 m is preferred over 1 hm (hectometre) or 10 dam (decametres). The prefixesdeci-andcenti-,and less frequentlyhecto-anddeca-,are generally used for informal purposes; the centimetre (cm) is especially common. Some modern building codes require that the millimetre be used in preference to the centimetre, because "use of centimetres leads to extensive usage of decimal points and confusion".^[10]These prefixes are also commonly used to create metric units corresponding to older conventional units, for examplehectaresandhectopascals.
Prefixes may not be used in combination on a single symbol. This includes the case of the base unit kilogram, which already contains a prefix. For example, milligram (mg) is used instead of microkilogram (μkg).
During mathematical operations, prefixes are treated as multiplicative factors. For example, 5 km is treated as 5000 m, which allows all quantities based on the same unit to befactored togethereven if they have different prefixes.
A prefix symbol attached to a unit symbol is included when the unit is raised to a power. For example, 1 km²denotes 1 km × 1 km = 10⁶m²,not 10³m².

Usage

Examples

The mass of anelectronis about 1 rg (rontogram).^[7]^[a]
The mass of 1 litre ofwateris about 1 kg (kilogram).^[12]
The mass of theEarthis about 6 Rg (ronnagrams).^[7]
The mass ofJupiteris about 2 Qg (quettagrams).^[7]

Examples of powers of units with metric prefixes

1 km²means onesquare kilometre,or theareaof asquareof1000 mby1000 m.In other words, an area of1000000square metresand not1000square metres.
2 Mm³means two cubicmegametres,or thevolumeof twocubesof1000000mby1000000mby1000000m,i.e.2×10¹⁸m³,and not2000000cubic metres(2×10⁶m³).

Examples with prefixes and powers

5 mV×5 mA=5×10⁻³V×5×10⁻³A=25×10⁻⁶V⋅A=25 μW.
5.00 mV+10 μV=5.00 mV+0.01 mV=5.01 mV.
5 cm=5×10⁻²m=5 × 0.01 m= 0.05 m.
9 km²=9 × (10³m)²=9 × (10³)²× m²=9×10⁶m²=9 ×1000000m²=9000000m².
3 MW =3×10⁶W= 3 ×1000000W=3000000W.

Micro symbol

Whenmegaandmicrowere adopted in 1873, there were then three prefixes starting with "m", so it was necessary to use some other symbol besides upper and lowercase 'm'. Eventually the Greek letter "μ" was adopted.

However, with the lack of a "μ" key on most typewriters, as well as computer keyboards, various other abbreviations remained common, including "mc", "mic", and "u".

From about 1960 onwards, "u" prevailed in type-written documents.^[b]BecauseASCII,EBCDIC,and other common encodings lacked code-points for " $μ$ ",this tradition remained even as computers replaced typewriters.

WhenISO 8859-1was created, it included the " $μ$ "symbol formicroat codepoint0xB5;later, the whole of ISO 8859-1 was incorporated into the initial version ofUnicode.But subsequently, Unicode version 6 deprecatedU+00B5in favour of the Greek letter " $μ$ "on codepointU+03BC.

Keyboard entry

Most keyboards do not have a " $μ$ "key, so it is necessary to use a key-code; this varies depending on the operating system, physical keyboard layout, and user's language.

For all keyboard layouts

OnMicrosoft Windowssystems,
- arbitrary Unicode codepoints can be entered in decimal with:Altsustained,0181,and releasingAlt.A leading "0" is required
  (this registers as the corresponding Unicode hexadecimal code-point, 0xB5 = 181.), or
- arbitrary Unicode codepoints can be entered in hexadecimal as:Alt++b5
  (up to 5 hexadecimal characters, not counting the leading '+', upper or lower case), or
- in the tradition of MS-DOS,IBM code page 437one can also enter old code-points in decimal:Alt+230
  (the leading zero must be omitted);
OnLinuxsystems,
- under X11, when aCompose keyhas been enabled:Composemu
- under X11, withibusversion 1.5.19 (or higher) active, and a non-composing input method selected: The default keybinding for starting codepoint input isCtrl+⇧ Shift+u.The key sequenceCtrl+⇧ Shift+ub5spacethen produces U+00B5, the micro sign.
- on the VGA console's virtual terminals like tty1: arbitrary Unicode codepoints can be entered in decimal as:Altsustained,181,and releasingAlt.A leading "0" is not required.

For QWERTY keyboard layouts

OnLinuxsystems,
- code-point U+00b5 can be entered asright-alt+m(provided the rightalt keyis configured to act asAltGr).
OnMacOSsystems, code-point U+00b5 can be entered as either⌥ Opt+mor⌥ Opt+Y.

Typesetting in Latex

TheLaTeXtypesetting system features anSIunitxpackage in which the units of measurement are spelled out, for example,
\qty{3}{\tera\hertz}formats as "3 THz".^[13]

Application to units of measurement

The use of prefixes can be traced back to the introduction of the metric system in the 1790s, long before the 1960 introduction of the SI.^{[citation needed]}The prefixes, including those introduced after 1960, are used with any metric unit, whether officially included in the SI or not (e.g., millidyne and milligauss). Metric prefixes may also be used with some non-metric units, but not, for example, with the non-SI units of time.^[14]

Metric units

Mass

The unitskilogram,gram,milligram,microgram, and smaller are commonly used for measurement ofmass.However, megagram, gigagram, and larger are rarely used;tonnes(and kilotonnes, megatonnes, etc.) orscientific notationare used instead. The megagram does not share the risk of confusion that the tonne has with other units with the name "ton".

The kilogram is the only coherent unit of theInternational System of Unitsthat includes a metric prefix.^[15]^: 144

Volume

Thelitre(equal to a cubic decimetre), millilitre (equal to a cubic centimetre), microlitre, and smaller are common. In Europe, the centilitre is often used for liquids, and the decilitre is used less frequently. Bulk agricultural products, such as grain, beer and wine, often use the hectolitre (100 litres).^{[citation needed]}

Larger volumes are usually denoted in kilolitres, megalitres or gigalitres, or else in cubic metres (1 cubic metre = 1 kilolitre) or cubic kilometres (1 cubic kilometre = 1 teralitre). For scientific purposes, the cubic metre is usually used.^{[citation needed]}

Length

The kilometre, metre, centimetre, millimetre, and smaller units are common. The decimetre is rarely used. The micrometre is often referred to by the older non-SI namemicron.In some fields, such aschemistry,theångström(0.1 nm) has been used commonly instead of the nanometre. Thefemtometre,used mainly in particle physics, is sometimes called afermi.For large scales, megametre, gigametre, and larger are rarely used. Instead, ad hoc non-metric units are used, such as thesolar radius,astronomical units,light years,andparsecs;the astronomical unit is mentioned in the SI standards as an accepted non-SI unit.^{[citation needed]}

Time

Prefixes for the SI standard unitsecondare most commonly encountered for quantities less than one second. For larger quantities, the system ofminutes(60 seconds),hours(60 minutes) anddays(24 hours) isaccepted for use with the SIand more commonly used. When speaking of spans of time, the length of the day is usually standardised to86400seconds so as not to create issues with the irregularleap second.^{[citation needed]}

Larger multiples of the second such as kiloseconds and megaseconds are occasionally encountered in scientific contexts, but are seldom used in common parlance. For long-scale scientific work, particularly inastronomy,theJulian yearorannum(a) is a standardised variant of theyear,equal to exactly31557600seconds (⁠365+ 1 /4⁠days). The unit is so named because it was the average length of a year in theJulian calendar.Long time periods are then expressed by using metric prefixes with the annum, such as megaannum (Ma) orgigaannum(Ga).^{[citation needed]}

Angle

The SI unit of angle is theradian,butdegrees,as well asarc-minutes and arc-seconds,see some scientific use.^{[citation needed]}

Temperature

Common practice does not typically use the flexibility allowed by official policy in the case of the degree Celsius (°C). NIST states:^[16]"Prefix symbols may be used with the unit symbol °C and prefix names may be used with the unit namedegree Celsius.For example, 12 m°C (12 millidegrees Celsius) is acceptable. "In practice, it is more common for prefixes to be used with thekelvinwhen it is desirable to denote extremely large or small absolute temperatures or temperature differences. Thus, temperatures of star interiors may be given with the unit of MK (megakelvin), and molecular cooling may be given with the unit mK (millikelvin).^{[citation needed]}

Energy

In use thejouleand kilojoule are common, with larger multiples seen in limited contexts. In addition, thekilowatt-hour,a composite unit formed from thekilowattand hour, is often used for electrical energy; other multiples can be formed by modifying the prefix of watt (e.g. terawatt-hour).^{[citation needed]}

There exist a number of definitions for the non-SI unit, thecalorie.There are gram calories and kilogram calories. One kilogram calorie, which equals one thousand gram calories, often appears capitalised and without a prefix (i.e.Cal) when referring to "dietary calories"in food.^[17]It is common to apply metric prefixes to the gram calorie, but not to the kilogram calorie: thus, 1 kcal = 1000 cal = 1 Cal.

Non-metric units

Metric prefixes are widely used outside the metric SI system. Common examples include themegabyteand thedecibel.Metric prefixes rarely appear withimperialorUSunits except in some special cases (e.g., microinch, kilofoot,kilopound). They are also used with other specialised units used in particular fields (e.g.,megaelectronvolt,gigaparsec,millibarn,kilodalton). In astronomy, geology, and palaeontology, theyear,with symbol 'a' (from the Latinannus), is commonly used with metric prefixes:ka,Ma, and Ga.^[18]

Official policies about the use of SI prefixes with non-SI units vary slightly between theInternational Bureau of Weights and Measures(BIPM) and the AmericanNational Institute of Standards and Technology(NIST). For instance, the NIST advises that "to avoid confusion, prefix symbols (and prefix names) are not used with the time-related unit symbols (names) min (minute), h (hour), d (day); nor with the angle-related symbols (names) ° (degree), ′ (minute), and ″ (second)",^[16]whereas the BIPM adds information about the use of prefixes with the symbolasfor arcsecond when they state: "However astronomers use milliarcsecond, which they denote mas, and microarcsecond, μas, which they use as units for measuring very small angles."^[19]

Non-standard prefixes

Distance marker on theRhineatRüdesheim:36 (XXXVI) myriametres fromBasel.The stated distance is 360 km; thedecimal markinGermanyis a comma.

Obsolete metric prefixes

Some of the prefixes formerly used in the metric system have fallen into disuse and were not adopted into the SI.^[20]^[21]^[22]The decimal prefix for ten thousand,myria-(sometimes speltmyrio-), and the earlybinary prefixes^{[broken anchor]}double-(2×) anddemi-(⁠1/2⁠×) were parts of the original metric system adopted by France in 1795,^[23]^[c] but were not retained when the SI prefixes were internationally adopted by the 11thCGPM conferencein 1960.

Other metric prefixes used historically includehebdo-(10⁷) andmicri-(10⁻¹⁴).

Double prefixes

Double prefixes have been used in the past, such asmicromillimetresormillimicrons(nownanometres),micromicrofarads(μμF; nowpicofarads,pF),kil Omega tonnes(nowgigatonnes),hectokilometres(now 100kilometres) and the derived adjectivehectokilometric(typically used for qualifying the fuel consumption measures).^[24]These are not compatible with the SI.

Other obsolete double prefixes included "decimilli-" (10⁻⁴), which was contracted to "dimi-"^[25]and standardised in France up to 1961.

There are no more letters of the Latin Alpha bet available for new prefixes (all the unused letters are already used for units). As such, Richard J.C. Brown (who proposed the prefixes adopted for 10^±27and 10^±30) has proposed a reintroduction of compound prefixes (e.g.kiloquetta-for 10³³) if a driver for prefixes at such scales ever materialises, with a restriction that the last prefix must always bequetta-orquecto-.This usage has not been approved by the BIPM.^[26]^[27]

Similar symbols and abbreviations

In written English, the symbolKis often used informally to indicate a multiple of thousand in many contexts. For example, one may talk of a40K salary(40000), or call theYear 2000 problemtheY2K problem.In these cases, an uppercase K is often used with an implied unit (although it could then be confused with the symbol for the kelvin temperature unit if the context is unclear). This informal postfix is read or spoken as "thousand", "grand", or just "k".

The financial and general news media mostly use m or M, b or B, and t or T as abbreviations for million, billion (10⁹) and trillion (10¹²), respectively, for large quantities, typically currency^[28]and population.^[29]

Themedicalandautomotivefields in the United States use the abbreviationsccorccmfor cubic centimetres. Onecubic centimetreis equal to onemillilitre.

For nearly a century, engineers used the abbreviationMCMto designate a "thousandcircular mils"in specifying the cross-sectional area of largeelectrical cables.Since the mid-1990s,kcmilhas been adopted as the official designation of a thousand circular mils, but the designationMCMstill remains in wide use. A similar system is used in natural gas sales in the United States:m(orM) for thousands andmm(orMM) for millions ofBritish thermal unitsortherms,and in the oil industry,^[30]whereMMbblis the symbol for "millions of barrels". This usage of the capital letterMfor "thousand" is fromRoman numerals,in whichMmeans 1000.^[31]

Footnotes

^m_e=9.1093837139(28)×10⁻³¹kg‍^[11].Converting to grams gives9.1093837015×10⁻²⁸g.Rounding to the nearest power of ten gives1×10⁻²⁷g,or 1 rg.
^ Sometimes the symbol 'u' is marked by adding a downstroke using a pen or pencil, or a slash '/u'.
^ "Art. 8. Dans les poids et mesures de capacité, chacune des mesures décimales de ces deux genres aura son double et sa moitié, afin de donner à la vente des divers objets toute la commodité que l'on peut désirer. Il y aura donc le double-litre et le demi-litre, le double-hectogramme et le demi-hectogramme, et ainsi des autres.

References

^"SI prefixes".Bipm.org.Bureau International des Poids et Mesures. Archived fromthe originalon 2014-09-12.Retrieved2023-06-13.
^"Resolutions of the General Conference on Weights and Measures (27th meeting)"(PDF)(in French and English). Bureau International des Poids et Mesures. 2022-11-18.Archivedfrom the original on 2023-06-13.Retrieved2024-05-18.
^^a ^b"On the extension of the range of SI prefixes".2022-11-18.Retrieved2023-02-05.
^"Metric (SI) Prefixes".NIST.
^Comptes rendus de la Quatorzième Conférence(in French). London:IUPAC.1947-07-24.
^"Resolution 12 of the 11th meeting of the CGPM".Bipm.org.Bureau International des Poids et Mesures. 1960. Archived fromthe originalon 2013-02-13.Retrieved2023-09-12.
^^a ^b ^c ^dSample, Ian (2022-11-18),"Earth weighs in at six ronnagrams as new prefixes picked for big and small",The Guardian,retrieved2022-12-14
^"Metric Prefixes and SI Units".learn.sparkfun.tutorials.Retrieved2020-01-26.
^"SI Unit rules and style conventions checklist".nist.gov.NIST.September 2004 [February 1998].
^Metric Design Guide(PDF)(Report). Public Buildings Service. U.S.General Services Administration.September 1995. PBS-PQ260. Archived fromthe original(PDF)on 2011-12-15.Retrieved2018-04-21– via National Institute of Building Sciences.
^"2022 CODATA Value: electron mass".The NIST Reference on Constants, Units, and Uncertainty.NIST.May 2024.Retrieved2024-05-18.
^"Kilogram | mass, weight, SI unit | Britannica".2024-03-15.
^Kottwitz, Stefan (2015-10-28),LaTeX Cookbook,Packt Publishing Ltd, pp. 158–9,ISBN 978-1-78439-630-5
^The International System of Units(PDF)(9th ed.), International Bureau of Weights and Measures, Dec 2022, p. 145,ISBN 978-92-822-2272-0
^The International System of Units(PDF)(9th ed.), International Bureau of Weights and Measures, Dec 2022,ISBN 978-92-822-2272-0
^^a ^bThompson, Ambler; Taylor, Barry N. (March 2008).Special Publication 811(Report) (2008 ed.).National Institute of Standards and Technology.Retrieved2018-06-21– via nist.gov.
^Conn, Carole; Kravitz, Len."Remarkable Calorie".University of New Mexico.Retrieved2017-05-22.
^Gargaud, Muriel; Amils, Ricardo; Cleaves, Henderson James (26 May 2011). "Ga".Encyclopedia of Astrobiology.Springer Science & Business Media. p. 621.ISBN 978-3-642-11271-3.
^The International System of Units (SI)(Report). SI Brochure. International Bureau of Weights and Measures.Retrieved2017-03-05.
^"H.R. 596, An Act to authorize the use of the metric system of weights and measures".29th Congress of the United States, Session 1. 1866-05-13. Archived fromthe originalon 2015-07-05.
^Brewster, David (1830).The Edinburgh Encyclopædia.Vol. 12. Edinburgh, UK: William Blackwood, John Waugh, John Murray, Baldwin & Cradock, J.M. Richardson. p. 494.Retrieved2015-10-09.
^Brewster, David (1832).The Edinburgh Encyclopaedia.Vol. 12 (1st American ed.). Joseph and Edward Parker.Retrieved2015-10-09.
^"La loi du 18 Germinal an 3".L'histoire du mètre[The History of the Metre] (in French).Archivedfrom the original on 2022-11-26.Retrieved2015-10-12– via histoire.du.metre.free.fr.Décision de tracer le mètre, unité fondamentale, sur une règle de platine. Nomenclature des « mesures républicaines ». Reprise de la triangulation[The Law of 18 Germinal [month], Year 3: Decision to draw the fundamental unit metre on a platinum ruler. Nomenclature of "republican measures". Resumption of the triangulation]
^Rowlett, Russ (2008) [2000]."millimicro-".How Many? A dictionary of units of measurement.University of North Carolina at Chapel Hill.Archivedfrom the original on 2016-08-29.Retrieved2016-08-29.
^Danloux-Dumesnils, Maurice (1969).The Metric System: A critical study of its principles and practice.The Athlone Press. p. 34.ISBN 9780485120134.Retrieved2015-10-09.(a translation of the French originalEsprit et bon usage du système métrique,1965 )
^Brown, Richard J.C. (2022-04-27). "Reply to" Facing a shortage of the Latin letters for the prospective new SI symbols: Alternative proposal for the new SI prefixes "".Accreditation and Quality Assurance.27(3): 143–144.doi:10.1007/s00769-022-01499-7.S2CID 248397680.
^Brown, Richard J.C. (2019). "Considerations on compound SI prefixes".Measurement.140:237–239.Bibcode:2019Meas..140..237B.doi:10.1016/j.measurement.2019.04.024.S2CID 146092009.
^"Obama unveils $3.8T budget proposal".Canadian Broadcasting Corporation. Associated Press. 2012-02-13.Retrieved2012-03-01.
^"More than 65M Flock to Discovery's Planet Earth".Multichannel.Retrieved2012-03-01.
^"Purcell, P (2007).Disambiguating M.PESA News 88 ".Pesa.au. Archived fromthe originalon 2012-03-25.Retrieved2012-03-01.
^"What is the difference between MCM and kcmil?".Reference. 2015-08-04.Retrieved2016-09-05.

External links

[3] Prefixes adopted before 1960 already existed before SI. The introduction of theCGS systemwas in 1873.

[13] _e=9.1093837139(28)×10⁻³¹kg‍^[11].Converting to grams gives9.1093837015×10⁻²⁸g.Rounding to the nearest power of ten gives1×10⁻²⁷g,or 1 rg.

[15] Sometimes the symbol 'u' is marked by adding a downstroke using a pen or pencil, or a slash '/u'.

[27] "Art. 8. Dans les poids et mesures de capacité, chacune des mesures décimales de ces deux genres aura son double et sa moitié, afin de donner à la vente des divers objets toute la commodité que l'on peut désirer. Il y aura donc le double-litre et le demi-litre, le double-hectogramme et le demi-hectogramme, et ainsi des autres.

[prefixes-1] "SI prefixes".Bipm.org.Bureau International des Poids et Mesures. Archived fromthe originalon 2014-09-12.Retrieved2023-06-13.

[res2022-2] "Resolutions of the General Conference on Weights and Measures (27th meeting)"(PDF)(in French and English). Bureau International des Poids et Mesures. 2022-11-18.Archivedfrom the original on 2023-06-13.Retrieved2024-05-18.

[newUnitAdoption-4] "On the extension of the range of SI prefixes".2022-11-18.Retrieved2023-02-05.

[5] "Metric (SI) Prefixes".NIST.

[6] Comptes rendus de la Quatorzième Conférence(in French). London:IUPAC.1947-07-24.

[res12-7] "Resolution 12 of the 11th meeting of the CGPM".Bipm.org.Bureau International des Poids et Mesures. 1960. Archived fromthe originalon 2013-02-13.Retrieved2023-09-12.

[earth-electron-8] Sample, Ian (2022-11-18),"Earth weighs in at six ronnagrams as new prefixes picked for big and small",The Guardian,retrieved2022-12-14

[9] "Metric Prefixes and SI Units".learn.sparkfun.tutorials.Retrieved2020-01-26.

[10] "SI Unit rules and style conventions checklist".nist.gov.NIST.September 2004 [February 1998].

[11] Metric Design Guide(PDF)(Report). Public Buildings Service. U.S.General Services Administration.September 1995. PBS-PQ260. Archived fromthe original(PDF)on 2011-12-15.Retrieved2018-04-21– via National Institute of Building Sciences.

[physconst-me-12] "2022 CODATA Value: electron mass".The NIST Reference on Constants, Units, and Uncertainty.NIST.May 2024.Retrieved2024-05-18.

[14] "Kilogram | mass, weight, SI unit | Britannica".2024-03-15.

[16] Kottwitz, Stefan (2015-10-28),LaTeX Cookbook,Packt Publishing Ltd, pp. 158–9,ISBN 978-1-78439-630-5

[17] The International System of Units(PDF)(9th ed.), International Bureau of Weights and Measures, Dec 2022, p. 145,ISBN 978-92-822-2272-0

[18] The International System of Units(PDF)(9th ed.), International Bureau of Weights and Measures, Dec 2022,ISBN 978-92-822-2272-0

[Special_Publication_811-19] Thompson, Ambler; Taylor, Barry N. (March 2008).Special Publication 811(Report) (2008 ed.).National Institute of Standards and Technology.Retrieved2018-06-21– via nist.gov.

[20] Conn, Carole; Kravitz, Len."Remarkable Calorie".University of New Mexico.Retrieved2017-05-22.

[21] Gargaud, Muriel; Amils, Ricardo; Cleaves, Henderson James (26 May 2011). "Ga".Encyclopedia of Astrobiology.Springer Science & Business Media. p. 621.ISBN 978-3-642-11271-3.

[22] The International System of Units (SI)(Report). SI Brochure. International Bureau of Weights and Measures.Retrieved2017-03-05.

[23] "H.R. 596, An Act to authorize the use of the metric system of weights and measures".29th Congress of the United States, Session 1. 1866-05-13. Archived fromthe originalon 2015-07-05.

[Brewster_1830-24] Brewster, David (1830).The Edinburgh Encyclopædia.Vol. 12. Edinburgh, UK: William Blackwood, John Waugh, John Murray, Baldwin & Cradock, J.M. Richardson. p. 494.Retrieved2015-10-09.

[Brewster_1832-25] Brewster, David (1832).The Edinburgh Encyclopaedia.Vol. 12 (1st American ed.). Joseph and Edward Parker.Retrieved2015-10-09.

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v t e SI units
Base units	ampere candela kelvin kilogram metre mole second
Derived units with special names	becquerel coulomb degree Celsius farad gray henry hertz joule katal lumen lux newton ohm pascal radian siemens sievert steradian tesla volt watt weber
Other accepted units	astronomical unit dalton day decibel degree of arc electronvolt hectare hour litre minute minute and second of arc neper tonne
See also	Conversion of units Metric prefixes Historical definitions of the SI base units 2019 redefinition System of units of measurement
Category

v t e Orders of magnitude
Quantity	Acceleration Angular momentum Area Bit rate Charge Computing Current Data Density Energy/Energy density Entropy Force Frequency Illuminance Length Luminance Magnetic field Mass Molarity Numbers Power Pressure Probability Radiation Sound pressure Specific heat capacity Speed Temperature Torque Time Voltage Volume
See also	Back-of-the-envelope calculation Best-selling electronic devices Fermi problem Powers of 10anddecades 10th 100th 1000000th Metric (SI) prefix Macroscopic scale Microscopic scale
Related	Astronomical system of units Earth's location in the Universe Cosmic View(1957 book) To the Moon and Beyond(1964 film) Cosmic Zoom(1968 film) Powers of Ten(1968 and 1977 films) Cosmic Voyage(1996 documentary) The Scale of the Universe(2010) Cosmic Eye(2012)
Category