Multiples and sub-multiples of units

Some quantities are far too big or too small to write easily in plain units, so we put a prefix in front of the unit. Each prefix is a multiplier.

• giga (G): 10⁹, one thousand million
• mega (M): 10⁶, one million
• kilo (k): 10³, which is 1000
• centi (c): 10^-2, one hundredth
• milli (m): 10^-3, one thousandth
• micro (μ): 10^-6, one millionth
• nano (n): 10^-9, one thousand millionth

So 1 kilometre is 1000 metres and 1 millimetre is one thousandth of a metre. Take care with capital and small letters: M means mega but m means milli. A power station with an output of 5 MW produces 5 million watts, because 1 MW = 1000000 W, so 5 MW = 5000000 W. Going the other way, a kettle rated at 3000 W can also be described as a 3 kW kettle.