How to use the Unit Converter
- Choose a category tab — length, weight, temperature, area, volume, speed, data size, time, energy or pressure.
- Type a value on the left and pick the units. The result appears on the right instantly; you can also type on the right to convert backwards.
- Use ⇄ to swap the units. The formula line shows the conversion factor.
- The table below converts your value into every unit of the category at once — click a row to make it the target unit.
How unit conversion works
Each category has a base unit — metres for length, kilograms for mass, bytes for data, pascals for pressure, joules for energy. Every unit is stored as an exact factor of that base (an inch is defined as exactly 0.0254 m, a pound as exactly 0.45359237 kg), so converting means multiplying into the base unit and dividing out to the target. Temperature is the exception: Celsius, Fahrenheit and Kelvin have different zero points, so they need an offset as well as a factor.
Common conversions
| From | To | Multiply by |
|---|---|---|
| inches | centimetres | 2.54 (exact) |
| miles | kilometres | 1.609344 (exact) |
| pounds | kilograms | 0.45359237 (exact) |
| US gallons | litres | 3.785411784 (exact) |
| mph | km/h | 1.609344 |
| kWh | megajoules | 3.6 (exact) |
| bar | psi | ≈ 14.5038 |
Temperature formulas
°F = °C × 9/5 + 32 and °C = (°F − 32) × 5/9. Kelvin is Celsius shifted by 273.15: K = °C + 273.15. −40 is the one temperature that is the same in Celsius and Fahrenheit; 37 °C body temperature is 98.6 °F.
KB vs KiB: decimal and binary data units
Storage and network units come in two systems. Decimal (SI) prefixes multiply by 1000: 1 kB = 1,000 bytes, 1 MB = 1,000,000 bytes, 1 GB = 109 bytes — used by drive manufacturers, macOS and network speeds. Binary (IEC) prefixes multiply by 1024: 1 KiB = 1,024 bytes, 1 MiB = 1,048,576 bytes, 1 GiB = 1,073,741,824 bytes — used by Windows (which labels them “KB/MB/GB”), RAM and most programming tools. That’s why a “1 TB” drive shows up as about 931 GB in Windows. Network speeds are in bits: a 100 Mbit/s connection downloads at most 12.5 MB per second (divide by 8).
US vs imperial volumes
A US gallon (3.785 L) is smaller than an imperial (UK) gallon (4.546 L), and US fluid ounces (29.57 ml) differ from UK fluid ounces (28.41 ml). Recipes and fuel figures from the UK and US therefore don’t match — pick the right unit in the Volume tab. For CSS units like px, rem and em, use the PX to REM Converter.
Tools that pair well with the Unit Converter
- Percentage Calculator — Seven everyday percentage calculations on one page.
- Number Base Converter — Type a number in any base and see it in all the others instantly.
- Time Zone Converter — Convert any time between cities and time zones, see the current time everywhere, and find a meeting slot that falls in everyone’s working hours.
- Date Difference Calculator — Count the days between two dates — including business days and a years/months/days breakdown — add or subtract time from a date, or run a live countdown.