Free converter

Free conversion calculator

A conversion calculator for length, weight, temperature, volume, speed and fifteen other categories: pick a category, type your value, and read it in every unit at once, metric and imperial side by side.

3.93700787
10 cm = 3.93700787 in ≈ 3 15/16 in

Formula: in = cm ÷ 2.54 10 ÷ 2.54 = 3.93700787

Tip: type a calculation, like 12+30 or 6×32.
In every unit (30)

How to use this conversion calculator

Start with the category above the field: length, weight, temperature, volume, area, speed, time, fuel economy, energy, and more specialized ones such as network bandwidth, illuminance in lux or the Beaufort wind scale. The conversion calculator carries the same units as the app, 320 of them, with the same conversion factors.

Then pick the unit you have and the unit you want, and type your value. The answer updates as you type, and the list below gives the same value in every unit of the category. The round button between the two units swaps them. You can also type a sum such as 3×250 or 12+30: the conversion calculator does the math first, then converts.

For the conversions people look up most, a dedicated page goes further, with the formula, common values and the usual traps: the cm to inches converter, the km to miles converter and the kg to lbs converter.

Metric or imperial: why we still convert

The United States measures in feet, pounds and degrees Fahrenheit, while almost everyone else uses meters, kilograms and degrees Celsius. A recipe from London, a bike frame from Italy or a weather report from Mexico all need translating, and that is what a conversion calculator is for.

Watch out for units that share a name. The US gallon (3.785 liters) is not the imperial gallon (4.546 liters), a US short ton is 2,000 pounds while a metric tonne is 1,000 kilograms, and the nautical mile (1,852 meters) has nothing to do with the statute mile. Both versions sit in the list under their full names, so you can pick the right one.

The definitions come from the reference texts: since 1959 the inch is exactly 2.54 cm and the pound exactly 0.45359237 kg, as the National Institute of Standards and Technology (NIST) states. The math keeps every decimal and only rounds for display.

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