Universal Unit Converter

29 kinds of units: length, area, weight and mass, volume, temperature, time, speed, running pace, fuel economy, pressure, energy, power, force, density, torque, flow rate, frequency, angle, illuminance, parts per million and percent, electric current, voltage, electric charge, reactive power, apparent power, reactive energy, data storage, data transfer rate, and Roman numerals. Metric, imperial and US customary units are all included.

Yes. It is free, with no sign-up and no limit on conversions. Everything is calculated in your browser, nothing is sent to a server, and your last category, units and precision are remembered on your device.

Pick a category such as Length, Weight or Volume, type a value under From and choose the two units. The result updates as you type, and you can also type under To to convert the other way. The swap button reverses the units, and the table under the converter lists your value in every unit of that category.

Multiply the Celsius temperature by 9/5 (1.8) and add 32, so 25 °C is 25 × 1.8 + 32 = 77 °F. To go back, subtract 32 and multiply by 5/9. Kelvin is Celsius plus 273.15. The converter shows the formula for every pair of temperature units.

A megabyte is 1,000,000 bytes, the decimal unit drive makers and network speeds use. A mebibyte is 1,048,576 bytes (1024 × 1024), the binary unit Windows and memory sizes use. That is why a 1 TB drive shows up as about 931 GiB. The Data storage category lists both kinds side by side.

Divide 235.215 by the miles per gallon figure for US gallons, or 282.481 for UK gallons, so 30 MPG (US) is about 7.84 L/100 km. One unit is distance per fuel and the other is fuel per distance, so the converter divides instead of multiplying.