About the Unit Converter
Nine categories are covered: length, mass, temperature, area, volume, speed, time, pressure and energy. Conversion factors use the exact legal definitions where they exist — the international inch is exactly 25.4 mm, the pound exactly 0.45359237 kg, the US gallon exactly 231 cubic inches (3.785411784 L) and the imperial gallon exactly 4.54609 L. Results are shown to 12 significant digits, and very large or small values switch to scientific notation.
Temperature is not a simple ratio, because the scales have different zero points. The tool converts through kelvin: °F = °C × 9/5 + 32, K = °C + 273.15, and Rankine is kelvin times 9/5. Values below absolute zero (−273.15 °C, −459.67 °F) are rejected. The formula for the pair you choose is shown under the result.
A few units have more than one definition, so the table names the one used: US and imperial volumes differ (a US pint is 473 mL, a UK pint 568 mL); a “calorie” is the thermochemical 4.184 J and food labels’ Calorie is the kilocalorie; a month is the average Gregorian month of 30.436875 days; the short ton (2000 lb) and long ton (2240 lb) are both listed next to the metric tonne; and Mach 1 is taken at sea level and 15 °C (340.294 m/s), since the speed of sound depends on temperature.
How to use it
- Choose a category, for example Length or Temperature.
- Enter a value and pick the units to convert from and to.
- Read the result and the conversion factor or formula under it.
- Scroll the table to see the value in every unit of the category, and copy what you need.