Unit Converter

What is the Unit Converter?

The Unit Converter switches between metric, imperial and US units across the categories that come up in daily life and work: length, weight and mass, volume, area, temperature, speed, time, data storage, pressure and energy. Pick a category, choose from and to units, type a value, and the result updates as you type, with the conversion factor shown so you can trust it. It uses exact defined factors (an inch is exactly 25.4 mm, a pound exactly 0.45359237 kg) rather than rounded approximations. It runs in your browser.

How to use it

1. Select a category.
2. Choose the unit you have and the unit you want.
3. Enter the value. Swap the direction with one click.

Conversions worth memorising

• 1 inch = 2.54 cm; 1 foot = 30.48 cm; 1 mile = 1.609 km.
• 1 kg = 2.2046 lb; 1 oz = 28.35 g.
• 1 US gallon = 3.785 L; 1 UK gallon = 4.546 L; 1 US cup = 236.6 mL.
• Celsius to Fahrenheit: multiply by 1.8 and add 32. Quick estimate: double it and add 30.
• 1 km/h = 0.621 mph; 1 knot = 1.852 km/h.

The exact factors for every unit, the mental shortcuts, and the traps (US versus imperial gallons and pints, tons versus tonnes, fluid ounces versus ounces, kilobytes of 1000 versus 1024) are in unit conversion done right.

Precision

Results are computed at full floating-point precision and displayed to a sensible number of significant figures for the category. For engineering or lab work, copy the full-precision value shown under the result. Temperature is the one category where conversion is an offset as well as a scale, which is why 0 °C is 32 °F, not 0.

Related tools

Convert speeds and running paces in more detail with the Speed Converter, convert number bases with the Binary to Decimal Converter, and convert times across zones with the Time Zone Converter.

Frequently asked questions

Are the factors exact?

Yes, for units with defined values. Historical or regional units that vary are noted on the tool.

Does it convert currencies?

No. Exchange rates change by the minute and need a live feed.

Which gallon is used?

Both US and UK gallons are listed separately; check you have chosen the right one.