How this calculator works
The word imperial covers two related but different systems. Imperial length and mass units match the international definitions of the inch and pound, which the United States also uses. Volume is where they part: the US gallon is 3.785411784 L, while the imperial gallon is 4.54609 L. This page converts through a base metric unit for each quantity, then into the imperial units that fit it. Length goes through metres, mass through kilograms, volume through cubic metres and area through square metres.
Formula
Length: inches = metres / 0.0254, feet = metres / 0.3048, yards = metres / 0.9144, miles = metres / 1609.344. Mass: pounds = kilograms / 0.45359237, ounces = kilograms / 0.028349523125. Volume: US gallons = cubic metres / 0.003785411784, imperial gallons = cubic metres / 0.00454609. Area: square feet = square metres / 0.09290304 and acres = square metres / 4046.8564224.
Worked example
1 m = 39.3701 in = 3.28084 ft = 1.09361 yd. 1 kg = 2.20462 lb = 35.2740 oz. 1 L = 0.264172 US gal = 0.219969 imperial gal. 1 m2 = 10.7639 ft2. 1 hectare = 2.47105 acres. 10 km = 6.21371 mi.
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Frequently asked questions
Is a US gallon the same as an imperial gallon?
No. The US gallon is 3.785411784 L and the imperial gallon is 4.54609 L, so the imperial gallon is about 20 percent larger. This page shows both for volume so the difference is explicit.
Does the United Kingdom use imperial units?
The United Kingdom uses a mix. Road distances and speed limits are in miles, beer is sold in pints, and body weight is often in stones, but most trade and engineering uses metric units. The UK pint is an imperial pint of 568.261 mL, not the US pint of 473.176 mL.
Why does the page show only a few imperial units?
These are the units most often needed for the selected quantity. A focused pair page for a specific unit, such as metres to feet, gives the full two-way treatment and a table of common values.
Are these conversions exact?
The inch, foot, pound and gallon definitions are exact. The page rounds the displayed value to six significant digits, so a chained conversion should use the original metric value rather than a rounded imperial one.