Comparing measurement systems

Length

Imperial system	Conversion	Metric system
Thousands of an inch (th)	1 th = 0.0254mm	Micro-millimetre (mmm)
Inch (in)	1 in = 25.4mm	Millimetres (mm)
Foot (ft)	1 ft = 30.48cm	Centimetres (cm)
Yard (yd)	1 yd = 0.9144m	Metres (m)
Chain (ch)	1 ch (22 yds) = 20.12m	Metres (m)
Furlong (fur)	1 fur (10 chains) = 201.17m	Metres (m)
Mile (M)	1 mile = 1.6km	Kilometres (km)

Area

To work out area, you need to multiply length by width. There are no easy conversions for area measurements, so the best thing to do is convert the length and width into the sorts of unit you want to use individually, and then multiply them together!

For example, if a part for an engine measured 3 inches by 12 inches, but you needed to know it’s area in metric units, you would do the following calculations:

1 in = 2.54cm

3 in = 7.2cm

12 in = 30.48cm

Area (metric) = 30.48cm X 2.54cm = 77.4192cm²

Volume

Just like with area, to work out volume you have to do a multiplication. You need to multiply length by width by depth. There aren’t any simple conversions for volume measurements either, so you need to do the same thing you did for area, converting length, width and depth into the sort of unit you want to use individually, before multiplying them together!

Weight

Imperial system	Conversion	Metric system
Ounce (oz)	1 oz = 32g	Gram (gr)
Pound (lb)	1 lb (16oz) = 0.453kg	Kilogram (kg)
Stone (st)	1 st (14lb) = 6.35kg	Kilogram (kg)
½ Hundred Weight (½ cwt)	1 ½ cwt = 25.4kg	Kilogram (kg)
Hundred Weight (cwt)	1 cwt = 50.8kg	Kilogram (kg)
Ton (ton)	1 ton = 1.016tonne	Tonne (tonne)

Capacity

Imperial system	Conversion	Metric system
Fluid Ounce (fl oz)	1 fl oz = 29.57ml	Millilitre (ml)
Pint (pt)	1 pt = 0.568l 1 l = 1.76pt	Litre (l)
Quart (qt)	1 qt = 1.1365l	Litre (l)
Gallon (gal)	1 gal = 4.546l	Litre (l)
Bushel (bsh)	1 bsh = 36.3687l	Litre (l)