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Pharmacology for Nurses

A | International System of Units

Pharmacology for NursesA | International System of Units

The International System of Units (abbreviated SI for Système Internationale) is a system of units of measurement that was established in 1960 and consists of base units and derived units of measurement. This system, more commonly known as the metric system, is periodically updated and maintained by the General Conference on Weights and Measures (GCWM).

The SI system is the most widely used measurement system internationally; however, the United States has not fully adopted the system. It continues to use the U.S. customary system of measurement, except in health care. The common base units and derived units include body mass index, length, mass, temperature, and volume. Table A1 shows the common units derived from the SI and used in health care. Table A2 shows the common prefixes for this system.

For additional information on the SI system, refer to the National Institute of Standards and Technology (NIST) website.

Measurement Name Symbol
Body mass index Kilogram per meter squared kg/m2
Length Meter m
Mass Gram g
Temperature Degrees Celsius °C
Volume Liter L
Table A1 Common SI Units (source:
Whole Units Decimal Units
Thousands Hundreds Tens SI Unit Tenths Hundredths Thousandths
1000 100 10 1 0.1 0.01 0.001
Kilo– Hecto– Deka– Meter
Deci– Centi– Milli–
Table A2 Common SI Prefixes (source:

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