ABSTRACT
In Europe and the UK, the units for measuring different properties are known as SI units.
SI stands for Syste`me Internationale. All units are derived from seven base units.
Base quantity Base unit Symbol
Time Second s Electrical current Ampere A Length Metre m Mass Kilogram kg Temperature Kelvin K Luminous intensity Candela cd Amount of substance Mole mol
S I - D E R I V ED UN I T S
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
Capacitance Farad F Electrical resistance Ohm 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
S I UN I T P R E F I X E S
Name Multiplier Prefix Power of 10
Tera 1000000000000 T 1 × 1012 Giga 1000000000 G 1 × 109 Mega 1000000 M 1 × 106 Kilo 1000 k 1 × 103 Unit 1 Milli 0.001 m 1 × 10−3 Micro 0.000001 m 1 × 10−6 Nano 0.000000001 h 1 × 10−9 Pico 0.000000000001 r 1 × 10−12
mA Milliamp = one thousandth of an ampere km Kilometre = one thousand metres mv Microvolt = one millionth of a volt GW Gigawatt = one thousand million watts kW Kilowatt = one thousand watts Calculator example 1 kilometre is 1 metre × 103 Enter into calculator 1 EXP 3 = (1000) metres 1000 metres is 1 kilometre × 10−3 Enter into calculator 1000 EXP −3 = (1) kilometre 1 microvolt is 1 volt × 10−6 Enter into calculator 1 EXP −6 = (1−06 or 0.000001) volts (note sixth decimal place).
