The International System of Units

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Basic unit is the meter (m), which equals 39.37 in.
Common Multiples and Subdivisions  
kilometer (km) 103 m
decimeter (dm) 10-1 m
centimeter (cm) 10-2 m
millimeter (mm) 10-3 m
micrometer (µm)* 10-6 m
nanometer (nm) 10-9 m
angstrom (Å) 10-10 m

*Also called the micron (µ)


Basic unit is the gram (g).
Common Multiples and Subdivisions  
kilogram (kg) 103 g (2.2 lb)
centigram (cg) 10-2 g
milligram (mg) 10-3 g
microgram (µg) 10-6 g
nanogram (ng) 10-9 g
picogram (pg) 10-12 g


Basic unit is the liter, which equals 1 cubic decimeter, dm3 (1.06 quart). A liter of water at its maximum density weighs almost 1 kg. Therefore, 1 ml (= 10-3 liter) of water weighs, for all practical purposes, 1 g. One cubic centimeter (cm3 or cc) is 10-3 dm3. Therefore, it is equal to 1 ml, and the units ml and cc are used interchangeably.


Basic unit is the Celsius (formerly known as centigrade) degree, oC. 0oC is the freezing point of water; 100oC is the boiling point of water. To convert from oC to oF (Fahrenheit) or vice versa: oF - 32 = 9/5 oC.

Useful Equivalents

1 inch = 2.54 cm
1 oz = 28.35 g
1 lb = 453.6 g
1 U.S. fluid oz = 29.57 ml
1 U.S. liquid qt = 0.946 liter (l)
1 pound per square inch (psi) = 6.89 kilopascals (kPa)
Radiation dose
1 millisievert (mSv) = 100 millirems (mrem)

Some Useful Constants and Conversion Factors

The gas constant: R = 2 cal / [(mole)(°K)]

The Faraday constant: F = 23,062 cal / [(mole)(volt)]

The natural logarithm, ln, = (2.303)(log10)


13 February 2012