About this calculator
Almost every metric-imperial conversion is a simple multiplication by a fixed factor. Temperature is the exception, because it includes an offset, which is why you cannot convert kelvin to Celsius by scaling alone.
How it works
Each category defines its units relative to a base unit, then divides to produce every equivalent at once. The output shows all units rather than just the target, which makes a conversion usable without coming back for a second one.
Frequently asked questions
How many ounces are in a pound?
One pound is exactly 16 ounces. This is part of the avoirdupois system, which is used for both US and UK customary weight, unlike the troy system used for precious metals.
How many litres are in a gallon?
A US gallon is 3.785 litres. A UK imperial gallon is 4.546 litres, about 20% larger. Specify which gallon you mean when precision matters.
What is the difference between mass and weight?
Mass is how much matter something contains and is measured in kilograms. Weight is the force gravity exerts on that mass, so it changes with location, which is why astronauts are weightless but not massless.
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32. So 100°C is 212°F. The reverse is subtract 32, then multiply by 5/9.
Is the metric system harder to use?
Only if you grew up entirely with imperial. Most countries that use metric find it more consistent, since there is usually only one common unit per type rather than several with awkward ratios.
Why do some countries still use imperial?
Historical inertia. The US adopted the customary system early and never fully transitioned, and the UK and Australia retained it despite legal metrication attempts. The UK has been officially metric since 1979 but imperial survives in informal use.