Unit Converter
Nine categories, more than 60 units, and live conversion tables that update as you type.
Convert between 9 categories — length, mass, volume, area, time, speed, angle, digital storage and temperature.
Why temperature is special
Most unit conversions are simple multiplications. One kilometre is 1000 metres, one inch is exactly 0.0254 metres. But temperature scales have different zero points, so converting between them requires both a multiplication and an addition. Celsius to Fahrenheit is F = C × 9/5 + 32, and Kelvin is just Celsius shifted by 273.15. The calculator handles all four scales (Celsius, Fahrenheit, Kelvin, Rankine) using a common Celsius pivot internally.
The base unit pivot trick
Every category has a single "base" unit. To convert from unit A to unit B, the converter first scales A to the base, then divides into B. That keeps the conversion table size linear in the number of units, rather than quadratic, and it is also why adding a new unit to the table is as easy as supplying a single conversion factor to the base.
SI vs imperial vs traditional
The site supports SI units (metre, kilogram, second), US customary units (foot, pound, gallon), UK units where they differ (the UK gallon is 4.546 L, the US gallon is only 3.785 L), and a handful of traditional units like the nautical mile and the stone. When in doubt, hover the unit name to see the exact conversion factor used.