How to use the unit converter
Unit conversion is one of the most frequently used little tools around — checking the inch marking on an imported product, following an overseas recipe given in pounds and ounces, or running into the difference between GiB and GB on a server spec sheet. The conversions themselves aren't hard, but the factors are easy to mix up, especially between imperial and Chinese traditional units.
The seven categories covered
- Length: metre, kilometre, centimetre, millimetre, micrometre, nanometre, inch, foot, yard, mile, nautical mile, chi, cun
- Weight: kilogram, gram, milligram, tonne, pound, ounce, jin, liang, qian, dan, stone
- Area: square metre, square kilometre, square centimetre, hectare, mu, square foot, square mile, acre
- Volume: cubic metre, litre, millilitre, gallon (US/UK), quart, pint, fluid ounce, cubic foot
- Temperature: Celsius, Fahrenheit, Kelvin, Rankine
- Data storage: byte, KB, MB, GB, TB, PB, distinguishing decimal (1000) from binary (1024)
- Time: nanosecond, microsecond, millisecond, second, minute, hour, day, week, month, year
The conversions people get wrong most often
GB and GiB are not the same thing. Drive manufacturers use decimal, so 1 GB = 1,000 MB; operating systems use binary, so 1 GiB = 1,024 MiB. That is why a drive labelled 1TB shows about 931 GiB in the OS. It isn't a short measure — it's a historic split between two standards. This tool gives both sets of results.
The jin and the liang. Under the modern Chinese standard 1 jin = 10 liang = 500 grams, but the old scale had 16 liang to a jin, which is where the idiom "half a jin, eight liang" comes from. This tool uses the current standard, 1 jin = 500 grams.
There are two gallons. 1 US gallon ≈ 3.785 litres, 1 UK gallon ≈ 4.546 litres — a difference of about 20%. This tool lists them separately so they don't get mixed up.
Temperature isn't a simple multiplier. Celsius and Fahrenheit are related by a linear transform, not a ratio. The formula is °F = °C × 9/5 + 32. Minus 40 degrees is the one place the two scales coincide, a coincidence often used to check a conversion.
There are two ounces. The avoirdupois ounce (general weight, about 28.35 g) differs from the troy ounce (precious metals, about 31.10 g). Gold is priced in troy ounces; the weight category here gives avoirdupois ounces, so be careful with precious-metal calculations.
Frequently asked questions
What precision are the results?
The calculation uses double-precision floating point, displayed to 6 significant figures with values near a whole number rounded. That is more than enough for everyday use, but if you need financial-grade precision, use a dedicated decimal library — floating point has inherent limits.
Why isn't 1 mile exactly 1.6 kilometres?
One mile is defined as exactly 1,609.344 metres. Once the international bureau of weights and measures fixed the inch-to-metre relationship, miles, feet and yards were all derived from the inch, so those are exact values rather than approximations — the numbers just don't look tidy.
Can I see several target units at once?
Yes. Enter a value and the "all units" panel lists the conversion for every unit in that category at the same time, so you don't have to switch one by one.
Why does data storage separate decimal and binary?
Because storage manufacturers and operating systems use different standards. Manufacturers label capacity on 1KB = 1,000 bytes; operating systems count on 1KiB = 1,024 bytes. This tool lists KB (decimal) and KiB (binary) separately so you can pick whichever fits the situation.