Unit Converter

What it does

The unit converter turns one value into every other unit of the same quantity at once. Pick a quantity such as length, mass or temperature, choose the unit you are starting from, and type a number. The table shows the result in all supported units side by side, so you can compare kilometers, miles and nautical miles, or Celsius, Fahrenheit and Kelvin, without switching back and forth.

Nine quantities are covered:

• Length: millimeter, centimeter, meter, kilometer, inch, foot, yard, mile and nautical mile.
• Mass: milligram, gram, kilogram, tonne, ounce, pound, stone and the Chinese jin.
• Temperature: Celsius, Fahrenheit and Kelvin.
• Volume: milliliter, liter, cubic meter, teaspoon, tablespoon, US fluid ounce, US cup, US gallon and UK gallon.
• Area: square centimeter, square meter, hectare, square kilometer, square foot, acre, square mile and the Chinese mu.
• Speed: meters per second, kilometers per hour, miles per hour, knots and feet per second.
• Time: millisecond, second, minute, hour, day, week and year (365 days).
• Pressure: pascal, kilopascal, bar, standard atmosphere, psi and millimeters of mercury.
• Energy: joule, kilojoule, calorie, kilocalorie, watt-hour, kilowatt-hour and BTU.

How to use

1. Choose a quantity in Quantity. The input unit resets to a sensible default for that quantity.
2. Choose the unit your number is in under From unit.
3. Type a value. Commas, spaces and underscores used as thousands separators are ignored, and scientific notation such as 1e6 works too.
4. Read the table, or copy any single row.

Example

Typing 42 with Length and Meter selected gives 4200 cm, 0.042 km, about 1653.54 inches, about 137.8 feet and about 0.0261 miles. Switch to Temperature, choose Celsius and type 100 to get 212 °F and 373.15 K.

Notes on precision

Linear units are converted through a base unit (meter, kilogram, liter and so on) using exact factors from international definitions. Temperature is different because the scales have different zero points, so values pass through Kelvin instead of a simple multiplication. Values below absolute zero are rejected because they do not exist physically.

Results are rounded to 12 significant digits to hide floating-point noise such as 0.30000000000000004. Very large or very small results switch to scientific notation so they stay readable.