Unit Converter
Convert between metric and US units for length, weight and temperature. Factors are exact by international definition — no rounded shortcuts.
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Frequently asked questions
How accurate are these conversions?
Length and weight factors are exact by international definition (for example, 1 inch = 25.4 mm exactly, 1 pound = 0.45359237 kg exactly). Temperature conversions are exact formulas.
Why do US units differ from UK units for some measures?
The US customary system and the British imperial system share names but diverge on some units — the most notable is the fluid gallon (3.785 L in the US vs 4.546 L in the UK). This tool uses US customary units by default.
What is the easiest way to convert temperatures?
Celsius to Fahrenheit: multiply by 9/5 and add 32. Fahrenheit to Celsius: subtract 32 and multiply by 5/9. For a quick mental estimate, double the Celsius value and add 30.