Unit Converter converts between metric, imperial/British, scientific and technical units across 30 categories, entirely in your browser. Type a value, pick a source and a target unit and read the result instantly — like a pocket calculator. This page explains how the keypad, the decimal setting and the all-units table work, and what to keep in mind for temperature and fuel economy.
Pick a category — from length, area, volume, mass and temperature to speed, time, data size and data rate, pressure, energy, power, force, angle, frequency, fuel economy, illuminance, luminance, acceleration, torque, density, flow rate, electric charge, current, voltage, resistance, capacitance, radioactivity, radiation dose and typography. Each category covers metric units, imperial/British units and, where they exist, scientific and technical units such as light years, parsecs, Mach, knots or Planck units.
Either type straight into the Value field or use the keypad below it, which is laid out like a pocket calculator. The field accepts loose input: 1.5, 1,5 and 1.000,5 all parse the way you expect — the last separator you type counts as the decimal mark and the other one is treated as thousands grouping. The keypad also has 00 for quick round numbers, C to clear, ⌫ to delete the last digit and ± to flip the sign.
Auto keeps up to 12 significant digits and drops the trailing zeros that floating-point maths tends to produce, so 1 m → 3.280839895 ft stays readable instead of printing dozens of digits; very large or very small results switch to scientific notation. If you need a fixed precision — for example a price or a measurement spec — choose 0 to 8 from the Decimals list and every result will be rounded to exactly that many decimal places.
The panel on the right converts your current value into every unit of the selected category at once. Click any row to make that unit the target of the big result above, or press the ⇄ swap button between the two dropdowns to exchange the source and target units. The small line under the result always shows the reference factor, for example 1 km = 0.621371 mi, so you can sanity-check the conversion. The list is grouped into labelled families — metric/SI, imperial/US and scientific or traditional — so you can see which kind of unit measures the quantity.
Most categories are a simple multiplication, but two need care. Temperature scales use an offset as well as a factor, because their zero points differ: 0 °C is 273.15 K and 32 °F, so converting is not a plain multiply. Fuel economy is inverted: litres per 100 km and miles per gallon (or km per litre) are reciprocals, so a lower l/100 km figure means a more efficient car. The conversion therefore divides rather than multiplies, and the tool handles that for you.
Unit symbols (m, ft, kg, °C, l/100km …) are shown exactly as in science and are never translated, so a formula stays unambiguous in every language; only the surrounding interface and the unit names follow the language you pick from the menu (English, German, French, Italian, Spanish). The counter in the corner is the same anonymous hit counter every tool in the suite uses. Everything else — every value you type and every conversion — stays in your browser: nothing is uploaded, logged or stored, which is why the app is marked green (Local). Questions or suggestions? Use the Feedback link — it opens the suite contact form with Unit Converter pre-selected.