Unit Converter

They come from the definitions of the units: the international inch (25.4 mm exactly), the avoirdupois pound (0.45359237 kg), the US gallon (231 cubic inches) and imperial gallon (4.54609 L), the IT calorie (4.1868 J) and BTU, the food calorie of food labels (4.184 kJ, the thermochemical kilocalorie), China's market units (1 尺 = 1/3 m, 1 平方尺 = 1/9 m², 1 亩 = 10,000/15 m², about 666.67 m², and 1 斤 = 0.5 kg), Hong Kong's catty (司马斤, 0.60478982 kg, as its Weights and Measures Ordinance, Cap. 68, defines it) with its tael (1/16 catty) and picul (100 catties), which Singapore used too (its kati of 1⅓ lb, less than 0.01 mg more, left its Weights and Measures Act in 2005; Hong Kong's chi and Taiwan's jin are defined otherwise and not listed), the mechanical horsepower, the standard atmosphere and so on. Results show up to 10 significant digits; the factor line shows 12. The month and year in the time category are Gregorian averages (30.436875 and 365.2425 days) and are marked as such.

Temperature scales have different zero points, so they use formulas (°F = °C × 9/5 + 32, K = °C + 273.15) rather than a factor. Fuel economy mixes inverse quantities: litres per 100 km goes down as miles per gallon goes up, so those are converted through litres per gallon and kilometres per mile. A value of 0 in an inverse unit shows as infinity.

Both: kB, MB, GB and TB are powers of 1000, as disk makers and the SI use; KiB, MiB, GiB and TiB are powers of 1024, as most operating systems report. Convert between them to see the difference (1 GB is about 0.931 GiB).

Yes. 1,234.5 and 1 234.5 are read as thousands groups, 3,5 as a decimal comma when there is no dot, 2e3 as 2000, and 3/4 or 1 1/2 as fractions. Full-width digits typed with a Chinese or Japanese input method (１０, １，２３４．５) are read as ordinary digits. Anything else is reported as not a number under the field.

Once the page has loaded, yes. Nothing is fetched while you convert.

No. The page loads a small script into your browser and every calculation runs on your device. You can check this yourself in the browser's network panel: after the page has loaded there are no upload requests. Closing the tab discards what you entered.

No. These basic tools are free, have no limits set by us and store nothing on our servers.

Nothing you open or type. While the tab is open, the tool pages keep a short list of the steps taken in it, in the tab's session storage: the step (page opened, started, succeeded, first success, used again or failed), the tool's name, the time, how many files were used and, for a failure, an error code; never a file name, the contents of a file or your text. It holds at most the latest 200 steps, and the browser deletes it when the tab closes. The page never sends it. Where a Report a problem button is shown, you can attach the last 20 steps to your report; nothing is attached unless you tick that box. In local storage the page keeps only choices you made: a Light or Dark theme until you choose System again, the language you picked with the EN / 中文 switch if it differs from your browser's language, and this tool in your recently used list if you switched that list on at the tools page.