Unit Converters: Length, Weight, Volume, Temperature

Metric, US customary and British imperial units side by side. Conversion factors are the exact defined values, and units that differ between countries, such as gallons and cups, are labeled clearly.

Metric, US customary and imperial

Most of the world uses metric units. The United States uses US customary units for many everyday measurements, and the United Kingdom still uses some imperial units, such as miles, pints and stones. Several units share a name but not a size: a US gallon (3.785 L) is smaller than an imperial gallon (4.546 L), and a US cup (about 237 mL) differs from a metric cup (250 mL). Our converters list these separately so you can pick the right one.

Exact factors

Since 1959 the inch, foot, yard and mile, and the pound and ounce, have been defined exactly in metric terms (1 in = 2.54 cm, 1 lb = 0.45359237 kg). The converters use these exact definitions. See methods and sources for the full list.

Quick pair converters

For the most common everyday conversions, the pair pages (cm to inches, kg to lbs, feet to meters and Celsius to Fahrenheit) convert in both directions as you type and include reference tables.