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# UCUM derived unit

UCUM derived units are units of measurement derived from the seven base units specified by the Unified Code for Units of Measure (UCUM).[1][dubious ] They can be expressed as a product of one or more of the base units, possibly scaled by an appropriate power of exponentiation.

The UCUM has special names for 20 of these derived units[disputed ] (for example, hertz, the UCUM unit of measurement of frequency), but the rest merely reflect their derivation: for example, the square metre (m2), the UCUM derived unit of area; and the gram per cubic metre (g/m3 or g m−3), the UCUM derived unit of density.

The names of UCUM derived units, when written in full, are in lowercase. However, the symbols for units named after persons are written with an uppercase initial letter. For example, the symbol for hertz is "Hz"; but the symbol for metre is "m".

## Derived units with special names

The Unified Code for units of measure assigns special names to 20 derived units.[disputed ] There are many SI derived units like the Newton that are defined in terms of the kilogram, the SI unit of mass. But the UCUM unit of mass is the gram, not the kilogram. So there are many units in the UCUM with prefixes like the millinewton.[2]

Named units derived from UCUM base units
Name Symbol Quantity Equivalents UCUM base unit
Equivalents
hertz Hz frequency 1/s s−1
millinewton mN force, weight g⋅m/s2 g⋅m⋅s−2
millipascal mPa pressure, stress mN/m2 g⋅m−1⋅s−2
millijoule mJ energy, work, heat mN⋅m
C⋅mV
mW⋅s
g⋅m2⋅s−2
milliwatt mW power, radiant flux mJ/s
mV⋅A
g⋅m2⋅s−3
ampere A[n 2] electric current C/s
mV/mΩ
mW/mV
mJ/mWb
C⋅s−1
millivolt mV voltage, electrical potential difference, electromotive force mW/A
mJ/C
g⋅m2⋅s−2⋅C−1
s/mΩ
g−1⋅m−2⋅s3⋅C2
milliohm electrical resistance, impedance, reactance 1/kS
mV/A
g⋅m2⋅s−1⋅C−2
kilosiemens kS electrical conductance 1/mΩ
A/mV
g−1⋅m−2⋅s1⋅C2
milliweber mWb magnetic flux C⋅mΩ
mJ/A
mT⋅m2
g⋅m2⋅s−1⋅C−1
millitesla mT magnetic induction, magnetic flux density mV⋅s/m2
mWb/m2
mN/(A⋅m)
g⋅s−1⋅C−1
millihenry mH electrical inductance mV⋅s/A
mΩ⋅s
mWb/A
g⋅m2⋅C−2
degree Celsius °C temperature relative to 273.15 K K K
lumen lm luminous flux cd⋅sr cd⋅rad2
becquerel Bq radioactivity (decays per unit time) 1/s s−1
gray Gy absorbed dose (of ionizing radiation) mJ/g m2⋅s−2
sievert Sv equivalent dose (of ionizing radiation) mJ/g m2⋅s−2
Notes
1. In the SI, both the radian and steradian are dimensionless derived units.
2. In the SI, the coulomb is derived from the ampere. 1 C = 1 A ⋅ 1 s

## Examples of derived quantities and units

Template:UCUM other units

## Other units used with UCUM

Some other units such as the hour, litre, tonne, bar and electronvolt are not UCUM units, but are widely used in conjunction with UCUM units.[citation needed]

• International Vocabulary of Metrology
• Metric prefix
• Metric system
• Planck units

## Bibliography

• I. Mills, Tomislav Cvitas, Klaus Homann, Nikola Kallay, IUPAC (June 1993). Quantities, Units and Symbols in Physical Chemistry (2nd ed.). Blackwell Science Inc. p. 72.CS1 maint: Multiple names: authors list (link) Search this book on