Unit Converter
Convert length, weight, temperature, volume, area, speed and data units instantly.
1 mm = 0.1 cm
One base unit per family, and why that matters
Every conversion here goes through a single reference unit for its family — meters for length, kilograms for weight, liters for volume — rather than through a stored answer for each pair. Converting inches to millimeters means going up to meters and back down, which is arithmetically identical to a direct factor but keeps one definition per unit instead of hundreds per combination. The practical upshot is that the numbers are consistent: inches to feet and feet to inches cannot disagree, because they are the same factor read in two directions.
Exact definitions, not rounded ones
Most imperial units have been defined in metric terms since 1959: an inch is exactly 25.4 mm, a pound is exactly 0.45359237 kg, and a mile is exactly 1609.344 m. Those are definitions rather than measurements, so the conversions built on them are exact to every digit shown. Where a unit genuinely is approximate, the imprecision is in the unit itself — the US gallon and the imperial gallon really are different sizes, which is why the volume list says which one it means.
Temperature is the one that works differently
Every other conversion is a multiplication, so doubling the input doubles the output. Temperature is not: Celsius and Fahrenheit have different zero points as well as different step sizes, so converting means scaling and shifting. That is why 0 °C is 32 °F rather than 0 °F, why 20 °C is not twice as warm as 10 °C in Fahrenheit terms, and why this converter shows no “1 °C = …” rate for temperature — a single multiplier would be the wrong shape for the question.
Kilobytes, kibibytes, and the missing disk space
The data family lists both decimal and binary units because both are in use and they do not agree. A kilobyte is 1000 bytes; a kibibyte is 1024. Drive manufacturers sell in decimal units while operating systems have traditionally reported in binary ones, and the gap widens as the numbers grow — 2.4% at kilobytes, about 10% at terabytes. That is the entire reason a “1 TB” drive shows up as roughly 931 GB once formatted: no space is missing, the two figures are counting in different bases.
Common conversions, one page each
These open the converter already set to the pair, with a reference table for the values people look up most: