# Converting between units of measurement

Measured quantities are frequently used in calculations. Each of these quantities has a basic unit.

Three examples are:

• Mass..................basic unit gram (the S.I. base unit for mass is kilogram)
• Liquid volume.......basic unit litre
• Time .................basic unit second

Quantities are measured in the basic unit and multiples of the basic unit, such as microgram or millilitre. 'Micro' and 'milli' are prefixes that represent a conversion factor from the basic unit.

## Commonly used prefixes

 Prefix (symbol) Conversion from basic unit Example Mega (M) multiply by 1 000 000 (x 106) 1.5 megaunits (Mu) =1.5 x 106 =1 500 000 units Kilo (k) multiply by 1000 (x 103) 2.25 kilogram (kg) = 2.25 x 1000 = 2250 gram (g) Basic unit no conversion needed (x10o) 7.5 gram (g) milli (m) divide by 1000 (÷ 103) 15 millilitre (mL) = 15 ÷ 1000 = 0.015 litre (L) micro (µ) divide by 1 000 000 (÷ 106) 55 microgram = 55 ÷ 106 = 0.000 055 gram (g)

Each unit differs from the one immediately above or below by a factor of 1000.

• When converting larger units to smaller units, multiply . You will have more smaller units than larger units.
• When converting smaller units to larger units, divide . You will have fewer larger units than smaller units.

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Converting between units - mass

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