Free online unit converter — length, weight, temperature, and more
Convert everyday measurements without a spreadsheet or a search box: centimetres to inches, kilograms to pounds, Celsius to Fahrenheit, megabytes to gigabytes, and litres to gallons. Pick a category, choose the two units, and type a value — the answer updates live as you type.
How to convert units
- Choose a Category: length, weight, temperature, data size, area, volume, or speed.
- Set the From and To units in the two dropdowns.
- Type a number into the Value box and read the answer in Result.
- Click Swap to flip the two units and convert back the other way.
Unit families you can convert
- Length — millimetres, centimetres, metres, kilometres, inches, feet, yards, miles.
- Weight — milligrams, grams, kilograms, tonnes, ounces, pounds.
- Temperature — Celsius, Fahrenheit, Kelvin.
- Data size — bytes, kilobytes, megabytes, gigabytes, terabytes.
- Area — square centimetres, metres, kilometres, inches, feet, plus hectares and acres.
- Volume and speed — millilitres, litres, cubic metres, cups, quarts, gallons; metres per second, kilometres per hour, miles per hour, knots.
Exact factors, not rounded shortcuts
Every category converts through a base unit using exact definitions — an inch is 0.0254 metres and a pound is 0.45359237 kilograms — so a value converted and converted back lands where it started. Temperature is the odd one out: Celsius, Fahrenheit, and Kelvin have offset scales, so real formulas apply instead of a single multiplier, which is why freezing water reads as 0, 32, and 273.15. Data sizes step in binary units of 1024, matching how operating systems report file and disk sizes.
Everything runs in your browser
No value is sent anywhere — the maths happens locally in JavaScript, with no sign-up and nothing stored. Need percentages rather than units? Open the percentage calculator, or work out an exact age in years, months, and days with the age calculator.
Need a custom tool or internal utility built for your team? Get in touch with SR Infobiz.