The following are the only units of measurement that are approved by the International System of Units (or SI for short). All other forms of measurement can be derived by using them in special equations.

Metric Units
 Name Symbol Measures Meter m Length Kilogram kg Mass Second s Time Ampere A Electric Current Kelvin K Thermodynamic Temperature Mole mol Amount of Substance Candela cd Luminous Intensity

These are the derived units that come from the standard units, and the equation for deriving them.

Derived Units
 Measured Unit Name Equation Area Square Meter m2 Volume Cubic Meter m3 Speed / Velocity Meter Per Second m/s Acceleration Meter Per Second Squared m/s2 Wave Number Reciprocal Meter m-1 Mass Density Kilogram Per Cubic Meter kg/m3 Specific Volume Cubic Meter Per Kilogram m3/kg Current Density Ampere Per Square Meter A/m2 Magnetic Field Strength Ampere Per Meter A/m Amount of Substance Concentration Mole Per Cubic Meter mol/m3 Luminance Candela Per Square Meter cd/m2 Mass Fraction Kilogram per Kilogram (1) kg/kg

Prefixes are placed in front of units in order to quickly and simply change the scale of measurement. This is the complete prefix table according to SI.

Metric Prefixes
 Factor Name Symbol Example 10 24 Yotta Y 1,000,000,000,000,000,000,000,000 10 21 Zetta Z 1,000,000,000,000,000,000,000 10 18 Exa E 1,000,000,000,000,000,000 10 15 Peta P 1,000,000,000,000,000 10 12 Tera T 1,000,000,000,000 10 9 Giga G 1,000,000,000 10 6 Mega M 1,000,000 10 3 Kilo k 1,000 10 2 Hecto h 100 10 1 Deka da 10 10 0 None - 1 10 -1 Deci d .1 10 -2 Centi c .01 10 -3 Milli m .001 10 -6 Micro µ .000001 10 -9 Nano n .000000001 10 -12 Pico p .000000000001 10 -15 Femto f .000000000000001 10 -18 Atto a .000000000000000001 10 -21 Zepto z .000000000000000000001 10 24 Yocto y .000000000000000000000001