Units
Unit converter
Twelve categories, 138 units and the formula always in sight. Pick a category and convert both ways as you type.
Conversions are worked out on your own machine. No sign-up, no waiting and nothing sent anywhere.
A converter is not much use if it hands you a number and leaves you wondering where it came from. This one shows the formula used underneath the result, so you can justify it in a report or check it by hand, and it lets you choose how many decimals to see, switching to scientific notation by itself when the number stops being readable.
The factors are exact by definition wherever possible: the inch is exactly 25.4 mm, the pound exactly 0.45359237 kg and the US gallon exactly 3.785411784 litres. The few that are conventional — the month, mach, the ton of TNT — are flagged as approximate rather than feigning precision.
Every category has its own page, with its units explained, its table of common equivalences and its own questions. Pick the one you need: