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Unit converter
Type a value, choose its unit and read the whole category at once, from nanometres to nautical miles. The factor tables travel with the page, so the arithmetic happens in this tab.
The result and the table below it update as you type. Nothing is rounded except what is printed — six significant digits — so a rounded figure is never carried into the next conversion.
How to convert units
Pick a category
Choose length, mass, temperature, area, volume, speed, data or pressure. The category decides which units the two pickers and the table offer, so pick it first.
Type the value
Enter a number in the from field and select its unit. Temperature is the one non-linear scale here: Celsius, Fahrenheit and Kelvin are converted through kelvin, not by a multiplier.
Read the table
The target field and every other unit in the category are computed from the same factor, so you can copy the unit you actually need without a second conversion.
How unit conversion actually works
Every unit in a category carries one number: how many base units it holds. Length counts in metres, mass in kilograms, volume in litres, data in bytes, pressure in pascals — so a conversion is the value multiplied by the source's factor and divided by the target's, with no intermediate rounding to drift. The definitions are the exact ones rather than approximations: a mile is 1609.344 m, an acre 4046.8564224 m², a pound 0.45359237 kg, an inch 0.0254 m by treaty.
Temperature is the exception, because its scales have origins instead of ratios: 0 °C is 273.15 K above absolute zero, and one Fahrenheit degree is five ninths of a kelvin. This page routes those through kelvin in both directions, which is why −40 °C and −40 °F land on the same number. Data is the other trap: decimal prefixes step by 1000 and binary ones by 1024, so both sets sit in the same picker and a 2 TB drive can be checked against its 1.8 TiB of usable space without leaving the page.
Unit conversion questions
Do my numbers go anywhere when I convert?
No. The unit tables are part of the page and the arithmetic runs in your browser, so a measurement you would rather not type into a website stays between you and your own machine. With the page already loaded, the converter also works with no network at all.
Why is temperature not just a multiplier?
Because the Celsius, Fahrenheit and Kelvin scales do not start at the same place: 0 °C is 273.15 K, while 0 K is absolute zero. A degree is a different size on each scale too, since a Fahrenheit step is five ninths of a kelvin, so both an origin and a ratio are involved — the page converts to kelvin and back out.
Should I read my drive in GB or GiB?
Manufacturers label storage in decimal units, where 1 GB is 1 000 000 000 bytes, while many operating systems report binary ones, where 1 GiB is 1 073 741 824 bytes. Both are in the Data picker, so comparing the label with what your file manager shows is one conversion rather than a search for a conversion table.
How large a number can I enter?
Any finite value, including negatives and decimals; results below 1e-6 or at 1e15 and above switch to exponent form so that very small and very large answers stay readable. Double precision carries the arithmetic and only the printed figure is rounded, to six significant digits.