Unit Converter
Convert length, weight, temperature, area, volume, speed, and time.
How to use
- Pick a category: length, weight, temperature, area, volume, speed, or time.
- Choose the unit on each side from the dropdowns.
- Type a value into either field — the opposite side converts instantly, in whichever direction you type.
- Use the swap button to reverse the two units.
- Or tap a quick-conversion chip (km→mi, kg→lb, °C→°F, cm→in, km/h→mph) to jump straight to a common pair.
About this tool
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Convert between metric and US/imperial units across seven everyday categories: length, weight, temperature, area, volume, speed, and time. The converter is fully bidirectional — type into either field and the other updates as you type — with a swap button and one-tap shortcuts for common pairs like km↔mi, kg↔lb, and °C↔°F. Results are shown to seven significant digits, and everything runs in your browser with your last conversion remembered locally.
Wherever a unit has an exact legal definition, the exact factor is used: the 1959 international yard and pound agreement fixed the inch at exactly 25.4 mm and the pound at 453.59237 g, the mile is exactly 1,609.344 m, and the US gallon exactly 3.785411784 L. Temperature is converted with the exact formulas rather than a multiplier, since °C, °F, and K have different zero points (K = °C + 273.15). Note that cup, pint, quart, and gallon here are US customary measures — the imperial (UK) gallon is a larger unit, about 4.546 L.
Frequently asked questions
Is the conversion two-way?
Yes. Both fields are editable: type a value on either side and the other recalculates immediately, so you never have to think about which direction counts as 'from'.
How accurate are the conversion factors?
Exact wherever an exact definition exists. Since the 1959 international yard and pound agreement, 1 inch = 25.4 mm and 1 lb = 453.59237 g by definition, so those conversions carry no error at all. Displayed results are rounded to seven significant digits.
How is temperature handled?
With the exact formulas rather than a simple factor: °F = °C × 9/5 + 32 and K = °C + 273.15. Kelvin is the SI base unit and starts at absolute zero, which is why 0 °C reads as 273.15 K.
Are the volume units US or imperial (UK)?
US customary. The gallon here is 3.785411784 L and the pint about 473 mL; imperial units with the same names are larger (an imperial gallon is about 4.546 L, an imperial pint 568 mL), so double-check which system a recipe or spec uses.
Does it work offline, and is anything stored?
All the math runs in your browser, so it keeps working with no connection once the page has loaded. Your last category, units, and value are saved in your browser's local storage on your device — nothing is sent to a server.
Guides on this topic
- Cups, Spoons and Ovens: Converting RecipesWhy a cup is not the same everywhere, why flour should be weighed, how to convert oven temperatures, and how to scale a recipe to another tin.
- Unit Conversion Traps: Gallons, Tons and DegreesUnits that share a name but not a size, why temperature differences convert differently, area and volume, fuel economy and false precision.
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