Unit converter
Convert between metric and imperial units, with every unit in the category shown at once.
Converting units
Most conversions multiply by a fixed factor. This tool converts through a base unit (meters for length, kilograms for mass, and so on), so any unit can be converted to any other without a separate formula for each pair.
Temperature is different
Celsius, Fahrenheit, and Kelvin do not share a common zero, so converting needs an offset as well as a scale. For example, °F = °C × 9/5 + 32 and K = °C + 273.15.
US and metric units
Gallons, pints, cups, and fluid ounces here are US customary units. Imperial (UK) units of the same names are different sizes. A year is taken as 365.25 days, and kilobyte means 1,000 bytes while kibibyte means 1,024.
Significant figures
Results show up to eight significant digits. In a lab or class report, round to the precision of your original measurement using the significant figures calculator.
Worked examples
Distance: 5 miles × 1.609344 km/mile = 8.047 km. Volume: 2.5 L = 2500 mL, and 2500 mL ÷ 29.5735 mL per US fluid ounce = 84.5 fl oz.
Temperature needs a formula, not just a factor: °C = (°F − 32) × 5/9, so 98.6 °F = (98.6 − 32) × 5/9 = 37.0 °C, and K = °C + 273.15.
Frequently asked questions
What do metric prefixes mean?
Each prefix is a power of ten: kilo (k) = 10³, centi (c) = 10⁻², milli (m) = 10⁻³, micro (µ) = 10⁻⁶ and nano (n) = 10⁻⁹. So 1 km = 1000 m and 1 mg = 0.001 g.
How do I convert units by hand?
Use dimensional analysis: multiply by conversion factors written as fractions so the unwanted units cancel. For example, 5 mi × (1.609 km ÷ 1 mi) = 8.05 km.
Why do fluid ounces and ounces differ?
A fluid ounce measures volume and an ounce measures mass. They only line up for water-like liquids, and even then only roughly.
How many significant figures should my answer have?
Keep the same number as your original measurement. Defined factors like 2.54 cm per inch are exact and don’t limit your answer.