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Detailed list of metric system
units, symbols, and prefixes


SI base units:

QuantityUnitSymbol
lengthmeterm
masskilogramkg
timeseconds
electric currentampereA
thermodynamic temperaturekelvinK
amount of substancemolemol
luminous intensitycandelacd


SI prefixes:

PrefixSymbolMultiplication factor
yottaY1024
zettaZ1021
exaE1018
petaP1015
teraT1012
gigaG1 000 000 000109
megaM1 000 000106
kilok1000103
hectoh100102
dekada10101
decid0.110-1
centic0.0110-2
millim0.00110-3
micro0.000 00110-6
nanon0.000 000 00110-9
picop10-12
femtof10-15
attoa10-18
zeptoz10-21
yoctoy10-24


SI derived units with special names and symbols:

QuantityNameSymbolExpression in terms of other SI units
angle, planeradian*radm/m = 1
angle, solidsteradian*srm2/m2 = 1
Celsius temperaturedegree Celsius°CK
electric capacitancefaradFC/V
electric charge, quantity of electricitycoulombCA·s
electric conductancesiemensSA/V
electric inductancehenryHWb/A
electric potential difference, electromotive forcevoltVW/A
electric resistanceohmΩV/A
energy, work, quantity of heatjouleJN·m
forcenewtonNkg·m/s2
frequency (of a periodic phenomenon)hertzHz1/s
illuminanceluxlxlm/m2
luminous fluxlumenlmcd·sr
magnetic fluxweberWbV·s
magnetic flux densityteslaTWb/m2
power, radiant fluxwattWJ/s
pressure, stresspascalPaN/m2
activity (referred to a radionuclide)becquerelBq1/s
absorbed dose, specific energy imparted, kermagrayGyJ/kg
dose equivalent, ambient dose equivalent, directional dose equivalent, personal dose equivalent, organ dose equivalentsievertSvJ/kg
catalytic activitykatalkatmol/s

* The radian and steradian, previously classified as supplementary units, are dimensionless derived units that may be used or omitted in expressing the values of physical quantities.


Units in Use with SI:

QuantityUnitSymbolValue in SI units
timeminutemin1 min = 60 s
hourh1 h = 60 min = 3600 s
dayd1 d = 24 h = 86 400 s
week, month, etc.
plane angledegree*°1° = (pi/180) rad
minute*'1' = (1/60)° = pi/10 800) rad
second*"1" = (1/60)' = (pi/648 000) rad
revolution, turnr1 r = 2 pi rad
areahectareha1 ha = 1 hm2 = 104 m2
volumeliter**L, l1 L = 1 dm3 = 10-3 m3
massmetric ton or tonne***t1 t = 103 kg

* Decimal degrees should be used for division of degrees, except for fields such as astronomy and cartography.
** The symbol L is preferred for use in the U.S.
*** The terms "metric ton" or "tonne" are restricted to commercial usage.


Units in Use Temporarily with SI:

NameSymbolValue in SI Units
nautical mile1 nautical mile = 1852 m
knot1 nautical mile per hour = (1852/3600) m/s
bar*bar1 bar = 100 kPa
barnb1 b = 100 fm2 = 10-28 m2
curieCi1 Ci = 3.7 x 1010 Bq
roentgenR1 R = 2.58 x 10-4 C/kg
radrad, rd**1 rad = 10 mGy = 10-2 Gy
remrem1 rem = 10 mSv = 10-2 Sv

* Use is limited to meteorology.
** When there is risk of confusion with the symbol for radian, rd may be used as the symbol for rad.


The above information has been compiled from various International System of Units (SI) reference publications.

For addition help see a selection of Metric posters, diagrams, and charts.


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Updated: 2013-06-17