How many in one?

Every page here answers one question in its first line, then gives you a converter, the formula and a table you can print. No sign-up, no popups, no waiting.

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Every value comes from an exact legal definition rather than a rounded constant: the inch is exactly 2.54 centimeters, the pound exactly 0.45359237 kilograms, the US gallon exactly 3.785411784 liters. The conversion code is covered by an automated test suite that checks known benchmarks and verifies that every unit converts back to its original value.

Read how we calculate for the full list of definitions and rounding rules, or browse all conversions on one page. Cooking? The printable kitchen conversion chart covers every measurement an American recipe uses.

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Last updated . Checked against the exact definitions on our how we calculate page.