Unit Conversion Factors Cheat Sheet

Exact conversion factors, computed from the legal definitions (the inch is exactly 25.4 mm and the pound exactly 0.45359237 kg; everything else follows). Values are shown to at most 13 significant figures. Use the Unit Converter Hub to convert any amount.

Length

Unit	Equals (SI)	Units per 1 of that SI unit
1 inch	0.0254 m	39.37008
1 foot	0.3048 m	3.28084
1 yard	0.9144 m	1.093613
1 mile	1609.344 m	0.0006213712
1 nautical mile	1852 m	0.0005399568

Mass

Unit	Equals (SI)	Units per 1 of that SI unit
1 ounce	0.028349523125 kg	35.27396
1 pound	0.45359237 kg	2.204623
1 stone (14 lb)	6.35029318 kg	0.157473
1 short ton (2,000 lb)	907.18474 kg	0.001102311
1 long ton (2,240 lb)	1016.0469088 kg	0.0009842065

Volume

Unit	Equals (SI)	Units per 1 of that SI unit
1 US teaspoon	4.92892159375 mL	0.2028841
1 US tablespoon	14.78676478125 mL	0.06762805
1 US fluid ounce	29.5735295625 mL	0.03381402
1 US cup	236.5882365 mL	0.004226753
1 US pint	473.176473 mL	0.002113376
1 US quart	946.352946 mL	0.001056688
1 US gallon	3.785411784 L	0.2641721
1 imperial gallon	4.54609 L	0.2199692

Area

Unit	Equals (SI)	Units per 1 of that SI unit
1 square foot	0.09290304 m²	10.76391
1 acre	4046.8564224 m²	0.0002471054
1 hectare	10000 m²	0.0001
1 square mile	2589988.110336 m²	0.0000003861022

Speed

Unit	Equals (SI)	Units per 1 of that SI unit
1 km/h	0.2777777777778 m/s	3.6
1 mile/hour	0.44704 m/s	2.236936
1 knot	0.5144444444444 m/s	1.943844

Energy and power

Unit	Equals (SI)	Units per 1 of that SI unit
1 calorie (thermochemical)	4.184 J	0.2390057
1 BTU (International Table)	1055.05585262 J	0.0009478171
1 kilowatt-hour	3600000 J	0.0000002777778
1 horsepower (mechanical)	745.6998715823 W	0.001341022
1 metric horsepower	735.49875 W	0.001359622

Pressure

Unit	Equals (SI)	Units per 1 of that SI unit
1 bar	100000 Pa	0.00001
1 atmosphere	101325 Pa	0.000009869233
1 psi	6894.757293168 Pa	0.0001450377
1 mmHg (torr)	133.3223684211 Pa	0.007500617

Temperature

Convert	Formula
°C to °F	°F = °C × 9/5 + 32
°F to °C	°C = (°F − 32) × 5/9
°C to K	K = °C + 273.15
°F to K	K = (°F − 32) × 5/9 + 273.15

Easy mistakes

US and imperial volumes differ. A US gallon is 3.785 L and an imperial gallon 4.546 L, about 20% larger.
Ton is not one thing. Metric tonne = 1,000 kg; short ton = 2,000 lb; long ton = 2,240 lb.
Calorie versus Calorie. The food Calorie is a kilocalorie (1,000 calories, 4.184 kJ).
BTU has variants. The value here is the International Table BTU; others differ by a fraction of a percent.
Mass is not weight. Pounds and kilograms measure mass; pound-force and newtons measure force.
Multiply or divide? Multiply by the first number column to go from the unit to SI; multiply by the last to go from SI to the unit.