Length

Metric Imperial
1 millimetre [mm] 0.03937 in
1 centimetre [cm] 10 mm 0.3937 in
1 metre [m] 100 cm 1.0936 yd
1 kilometre [km] 1000 m 0.6214 mile
Imperial Metric
1 inch [in] 2.54 cm
1 foot [ft] 12 in 0.3048 m
1 yard [yd] 3 ft 0.9144 m
1 mile 1760 yd 1.6093 km
1 int nautical mile 2025.4 yd 1.853 km

Area

Metric Imperial
1 sq cm [cm2] 100 mm2 0.1550 in2
1 sq m [m2] 10,000 cm2 1.1960 yd2
1 hectare [ha] 10,000 m2 2.4711 acres
1 sq km [km2] 100 ha 0.3861 mile2
Imperial Metric
1 sq inch [in2] 6.4516 cm2
1 sq foot [sq ft] 144 in2 0.0929 m2
1 sq yd [yd2] 9 sq ft 0.8361 m2
1 acre 4840 yd2 4046.9 m2
1 sq mile [mile2] 640 acres 2.59 km2

Volume

Metric Imperial
1 cu cm [cm3] 0.0610 in3
1 cu decimetre [dm3] 1,000 cm3 0.0353 ft3
1 cu metre [m3] 1,000 dm3 1.3080 yd3
1 litre [l] 1 dm3 1.76 pt
1 hectolitre [hl] 100 l 21.997 gal
Imperial Metric
1 cu inch [in3] 16.387 cm3
1 cu foot [ft3] 1,728 in3 0.0283 m3
1 fluid ounce [fl oz] 28.413 ml
1 pint [pt] 20 fl oz 0.5683 l
1 gallon [gal] 8 pt 4.5461 l
USA
measure
Metric
1 fluid ounce 1.0408 uk fl oz 29.574 ml
1 pint (16 fl oz) 0.8327 uk pt 0.4731 l
1 gallon 0.8327 uk gal 3.7854 l

Mass

Metric Imperial
1 milligram [mg] 0.0154 grain
1 gram [g] 1,000 mg 0.0353 oz
1 kilogram [kg] 1,000 g 2.2046 lb
1 tonne [t] 1,000 kg 0.9842 ton
Imperial Metric
1 ounce [oz] 437.5 grain 28.35 g
1 pound [lb] 16 oz 0.4536 kg
1 stone 14 lb 6.3503 kg
1 hundredweight [cwt] 112 lb 50.802 kg
1 long ton (uk) 20 cwt 1.016 t

Temperature

To convert from Celsius to Fahrenheit, firstmultiply by 9/5, then add 32.

To convert from Fahrenheit to Celsius, first subtract 32, then multiply by 5/9

Some common tempatures

°C °F Description
100 212 Water boils
40 104 Hot Bath
37 98.6 Body temperature
30 86 Beach weather
21 70 Room temperature
10 50 Cool Day
0 32 Freezing point of water
-18 0 Extremely Cold Day
-40 -40 Stupidly Cold (and the same number!)

(bold are exact)