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Unit converter

Pick a category and convert between units instantly, everything runs in your browser.

How Unit converter works

The unit converter handles everyday conversions across eight categories: length, mass and weight, temperature, volume, area, speed, digital data, and time. Choose a category, select the from and to units, type a value, and the result updates immediately. Metric and imperial units are both covered (cm to in, kg to lb, km/h to mph, Celsius to Fahrenheit, and many others). Nothing leaves your browser.

Factor-based categories use exact internationally-defined ratios (for example, one inch is exactly 0.0254 m by international agreement in 1959), while temperature requires adding or subtracting offsets rather than just multiplying, and that is handled correctly for all three scales.

Written by Bastien Sulyan

How to use Unit converter, step by step

  1. Select a category from the drop-down (length, mass, temperature, volume, area, speed, data, or time).
  2. Choose the unit you are converting from.
  3. Choose the unit you are converting to.
  4. Type the value in the input field.
  5. Read the converted result immediately; change any field and the result updates live.

Common use cases

  • Converting a US recipe that lists cups and ounces into grams and millilitres for a metric kitchen.
  • Checking a speed-limit sign in km/h when you are driving in a country that uses mph and your car's speedometer shows metric.
  • Converting a file size from megabytes to gigabytes when a cloud storage plan is quoted in different units.
  • Working out the area of a room in square feet when the estate agent's listing uses square metres.

Frequently asked questions

Which categories and units are supported?

Length (metre, kilometre, mile, yard, foot, inch, centimetre, millimetre, nautical mile); mass and weight (gram, kilogram, pound, ounce, tonne, stone); temperature (Celsius, Fahrenheit, Kelvin); volume (litre, millilitre, cubic metre, US gallon, UK gallon, US fluid ounce, cup, tablespoon, teaspoon); area (square metre, square kilometre, square mile, square yard, square foot, square inch, hectare, acre); speed (m/s, km/h, mph, knot); digital data (bit, byte, kilobyte through to terabyte in both SI and binary); and time (millisecond through to year).

How is temperature converted?

Temperature conversions account for the offset between scales. Celsius to Fahrenheit: multiply by 9/5 then add 32. Fahrenheit to Celsius: subtract 32 then multiply by 5/9. Celsius to Kelvin: add 273.15. Example: 100 degrees Celsius equals 212 degrees Fahrenheit and 373.15 Kelvin.

Are the conversion factors exact?

Yes for all factor-based categories. The 1959 international yard and pound agreement defined 1 inch as exactly 0.0254 m and 1 pound as exactly 0.453 592 37 kg. The tool uses these exact values, not rounded approximations.

Does it send my data anywhere?

No. All conversions are arithmetic operations executed locally in your browser. Nothing is uploaded and the tool works with no internet connection once the page has loaded.

What is the difference between SI (decimal) and binary units for digital data?

In SI (metric) notation, 1 kilobyte = 1000 bytes and 1 megabyte = 1 000 000 bytes. In binary notation, 1 kibibyte = 1024 bytes and 1 mebibyte = 1 048 576 bytes. Hard drive manufacturers use SI, while operating systems often report sizes in binary units, which causes the apparent size discrepancy you see when a new drive is formatted.

Can I use this for cooking or recipe conversions?

For straightforward volume-to-volume conversions (such as cups to millilitres) this tool gives exact results. For volume-to-weight conversions (such as cups of flour to grams) you need a cooking converter that accounts for ingredient density, because a cup of flour and a cup of honey have very different masses.

Do I need an account to use the unit converter?

No. There is no sign-up, no account and no usage limit. Every conversion is a plain arithmetic calculation running in your browser.

Can I use the unit converter on my phone?

Yes. It is a simple form with a live result, which works the same on a mobile browser as on a desktop one, and is arguably more useful on a phone since that is where you need a quick conversion while shopping or cooking.

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