All units are derived from seven base units.
Time Seconds
Electrical current Ampere A
Length Metre m
Mass Kilogram kg
Temperature Kelvin K
Luminous intensity Candela cd
Amount of substance Mole mol
SI-derived units Derived quantity Name Symbol
Frequency Hertz Hz
Force Newton N
Energy, work, quantity of heat
Joule J Electric charge,
quantity of electricity Coulomb C
Power Watt W
Potential difference,electromotive force Volt V or U
electrical symbols IEEE
Capacitance Farad F
Electrical resistance Ohm Ω
Magnetic flux Weber Wb
Magnetic flux density Tesla T
Inductance Henry H
Luminous flux Lumen cd
Area Square metre m2
Volume Cubic metre m3
Velocity, speed Metre per second m/s
Mass density Kilogram per cubic metre kg/m3
Luminance Candela per square metre cd/m2
SI unit prefixes Name Multiplier Prefix
Power of 10 Tera 1000 000 000 000 T 1×1012
Giga 1000 000 000 G 1×109
Mega 1000 000 M 1×106
Kilo 1000 k 1×103 Unit 1
Milli 0.001 m 1×10−3
Micro 0.000 001 m 1×10−6
Nano 0.000 000 001 n 1×10−9
Pico 0.000 000 000 001 ρ 1×10−12
Examples mA Milliamp = one thousandth of an ampere
km Kilometre = one thousand metres
μv Microvolt = one millionth of a volt
GW Gigawatt = one thousand million watts kW Kilowatt = one thousand watts