Unit Converter (length, weight, temp & more)
Pick a category, enter a value, and the converted result updates live. Six categories, dozens of units — all in your browser.
How it works
Choose a category, type the value you have, and select the source and target units. The result appears instantly. For most categories the tool converts your value to a base unit, then from the base unit to the target — so every pairing is covered. Temperature uses dedicated formulas because its zero points differ.
Categories and units
Length: metre, kilometre, centimetre, millimetre, mile, yard, foot, inch. Weight: kilogram, gram, milligram, tonne, pound, ounce. Temperature: Celsius, Fahrenheit, Kelvin. Area: m², km², cm², hectare, acre, square foot. Volume: litre, millilitre, cubic metre, gallon (US), quart, pint, cup, fluid ounce. Speed: m/s, km/h, mph, knot, ft/s.
FAQ
Are the conversion factors exact?
They use standard SI and US customary definitions (e.g. 1 inch = 25.4 mm exactly, 1 pound = 0.45359237 kg exactly). Results are rounded to 8 significant figures for readability.
Why is temperature handled separately?
Unlike length or weight, temperature scales have different zero points, so a
simple multiplication factor does not work. The tool converts through Celsius as
an intermediate: C → F is C × 9/5 + 32, C → K is C + 273.15.
Can I convert in either direction?
Yes. Set "From" and "To" to any pair in the category; the result is symmetric — converting 1 km to miles then back gives 1 km again.
How to use the unit converter
- Choose a category — length, weight, temperature, volume, area, speed, time or data size.
- Type a number into either field. The other field converts as you type, in both directions.
- Pick the source and target units from the two dropdowns; switching either one re-converts immediately.
- Need several results? Change the target unit repeatedly instead of retyping the value — the source number stays put.
How the conversions are calculated
Each category has one canonical base unit (metres for length, kilograms for mass, square metres for area, bytes for data). Every listed unit is defined once as a factor relative to that base, and a conversion is a multiply by the source factor followed by a divide by the target factor — which is why no conversion table between every possible pair is needed, and why the result is identical in both directions. Temperatures are the exception: Celsius, Fahrenheit and Kelvin are related by offsets and scales, not by a simple ratio, so they are converted with their own formulae.
Units and conventions used
The converter uses standard international definitions: 1 inch is exactly 25.4 mm, 1 pound is exactly 0.45359237 kg, 1 US gallon is 3.785411784 litres, 1 mile is 1609.344 m. Note that a US gallon differs from an imperial gallon — check which one your source means before trusting a recipe or a fuel figure. Data sizes use binary multiples (1 KiB = 1024 bytes), which is what operating systems report; storage manufacturers usually advertise decimal multiples (1 kB = 1000 bytes), which is why a "1 TB" drive shows as about 931 GB.
Troubleshooting
- Result reads 0 or blank: the input field contains text or a thousands separator. Type plain digits with a decimal point only.
- Temperature looks wrong: make sure you selected a temperature category — applying a ratio to Celsius and Fahrenheit gives nonsense because of the 32° offset.
- Too many decimal places: round it yourself; the converter does not round so you can see the exact value.
- Category not listed: currency and highly specialised units are deliberately excluded, since they need live rates or domain context.
FAQ
Is the result exact?
Within floating-point precision, yes. Definitions are exact where an exact definition exists; only the final display is subject to rounding.
Can I use it offline?
Yes. Once the page has loaded, every calculation happens locally with no network request, so it works on a plane or in a basement.
Why is my hard drive smaller than advertised?
Decimal vs binary units, as described above — the drive is correct, the marketing unit is just a different one.
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