Unit Converter

Convert length, weight, temperature, volume and speed between metric and imperial units — in real time, with exact conversion factors.

Popular Conversions

Dedicated pages for the most-searched conversions, each with a quick calculator and a reference table.

kg to lbs · lbs to kg · cm to inches · inches to cm · km to miles · miles to km · Celsius to Fahrenheit · Fahrenheit to Celsius · liters to gallons · gallons to liters · mph to km/h · km/h to mph

How to Convert Units

Three steps, all in your browser.

1

Choose a category

Pick Length, Weight, Temperature, Volume or Speed from the tabs. The unit dropdowns update to show the relevant units for that category.

2

Select units and type

Choose your "from" and "to" units, then type a value. The result appears instantly and works both ways — edit either side. Working with colors instead? Open the Color Converter.

3

Swap if you need the reverse

Tap the swap button to flip the conversion direction. Need to reformat some text too? The Case Converter is one tab away.

Frequently Asked Questions

What units can I convert?
The unit converter covers five categories. Length includes meters, kilometers, centimeters, millimeters, miles, yards, feet, inches and nautical miles. Weight includes kilograms, grams, milligrams, tonnes, pounds, ounces and stone. Temperature converts between Celsius, Fahrenheit and Kelvin. Volume includes liters, milliliters, cubic meters and US gallons, quarts, pints, cups and fluid ounces. Speed includes meters per second, kilometers per hour, miles per hour, knots and feet per second. Pick a category tab, choose your "from" and "to" units, and the result updates as you type.
How accurate are the conversions?
Every conversion uses the exact, internationally defined factor rather than a rounded approximation. One inch is exactly 0.0254 meters, one pound is exactly 0.45359237 kilograms, one US gallon is exactly 3.785411784 liters, and one mile is exactly 1609.344 meters. Temperature uses the precise formulas — for example Fahrenheit to Celsius is (F − 32) × 5 ÷ 9. Results are calculated at full double precision and then displayed to eight significant figures with trailing zeros trimmed, so what you see is accurate enough for engineering, cooking, travel and schoolwork alike.
Does it convert as I type?
Yes. The conversion is live and bidirectional. Type a number in the left box and the right box updates instantly; type in the right box and the left box updates instead. Changing either unit dropdown re-runs the conversion immediately. There is no convert button to press and no page reload — the math runs in your browser on every keystroke, so you get an answer the moment you finish typing.
What does the swap button do?
The swap button in the middle reverses the direction of the conversion by exchanging the "from" and "to" units. If you were converting kilometers to miles, one tap switches it to miles to kilometers and recalculates using the current value. It is a quick way to flip a conversion you do often without re-selecting both dropdowns, and it works the same way across all five categories.
Is the unit converter free and private?
Yes. The tool is completely free with no account, no sign-up and no limits, and every calculation happens locally in your browser. The numbers you enter are never sent to a server or stored, so there is nothing to log and nothing to leak. Once the page has loaded it even works offline, which makes it handy on a plane or anywhere with a poor connection.