Unit Converter
Type a number in either box to convert it, with the exact formula shown and the answer rounded to the significant figures you choose.
Type in either box. Worked out on your device; nothing is sent or saved.
Convert units exactly, and see how it’s done
Recipes, maps, labels and spec sheets mix metric and US units, and a factor rounded too early can throw an answer off. This converter works from each unit’s definition instead: an inch is exactly 2.54 centimeters and a US gallon exactly 3.785411784 liters, so the only rounding is the one you choose for the answer.
How to use it
- Pick what to convert: length, area, volume, mass, temperature, speed, time or digital storage.
- Choose a unit for each box.
- Type a number in either box, and the other box shows the conversion. Swap turns the pair around.
- Choose how many significant figures the answer shows.
Reading the result
- = or ≈: an equals sign means the answer is exact; ≈ means it was rounded to your figures. When the exact value is short, it’s shown too: 1 mile ≈ 1.60934 kilometers, exactly 1.609344.
- The formula gives the multiplier or divisor used, and each unit’s definition is listed with its source.
- Very large or small numbers appear in scientific notation, such as 6.21371 × 10⁻⁷. You can type them that way too: 6.2e-7.
Kilobytes and kibibytes
Data sizes are counted two ways. Kilo, mega and giga mean powers of 1,000; kibi, mebi and gibi (KiB, MiB, GiB) mean powers of 1,024. So 500 GB is about 465.661 GiB: the same bytes, counted in bigger steps. Both kinds are in the list, labeled, along with bits, kilobits, megabits and gigabits.
Good to know
- Temperatures are readings, not differences: 10 °C is 50 °F, but a rise of 10 °C is a rise of 18 °F.
- US and imperial gallons, pints and fluid ounces differ, so each is listed by name.
- Typing numbers: commas between groups of three are fine (1,250), but use a point for decimals. 1,5 is refused rather than guessed at.
- No cups to grams: that depends on the ingredient, so the tool converts volume to volume and mass to mass only.
- Time zones are a different job: the Time Zone Converter handles them.
Where the numbers come from
The SI Brochure (BIPM, 9th edition), NIST Special Publication 811 and NIST Handbook 44, the UK Weights and Measures Act 1985 for imperial volumes, IEC 80000-13 for data units, and ISO 8601 for weeks and years. The acre is the international acre of 43,560 square feet.