Free Unit Converters
20 accurate unit converters covering length, weight, temperature, area, volume, speed, pressure, energy, power, data storage, cooking measurements and shoe sizes. Conversion factors follow SI, NIST and BIPM references — every tool runs entirely in your browser.
About unit converters
Unit conversion looks trivial until you need to switch between metric and imperial, deal with US versus UK gallons, or convert temperatures where the relationship is offset as well as scaled. Every converter on this page uses internationally recognised conversion factors and clearly shows the formula applied, so you can trace exactly how the result was produced.
Conversion factors are taken from SI, NIST and BIPM references. Where US and UK variants differ — gallons, fluid ounces, shoe sizes — both units are available as separate options so you always convert to the correct one. Read the guide on converting temperature units for a deeper explanation of the mathematics behind the temperature converter.
Everyday Conversions
The most-used converters: length, weight and temperature.
Length Converter
Convert between metres, feet, inches, miles, kilometres, centimetres and more.
Distance Converter
Convert between miles, kilometres, nautical miles and related distance units.
Weight Converter
Convert between kilograms, pounds, ounces, stones, grams and tonnes.
Mass Converter
Convert between mass units including grams, ounces, kilograms and metric tonnes.
Temperature Converter
Convert between Celsius, Fahrenheit, Kelvin, Rankine and Réaumur.
Area Converter
Convert between square metres, square feet, acres, hectares and more.
Volume Converter
Convert between litres, millilitres, gallons, cubic metres and cubic feet.
Speed Converter
Convert between km/h, mph, m/s, ft/s and knots.
Scientific & Engineering Units
Pressure, energy, power, force, torque and density conversions.
Pressure Converter
Convert between pascals, bars, PSI, atmospheres, torr and millibars.
Energy Converter
Convert between joules, calories, kilocalories, kWh, BTU and electronvolts.
Power Converter
Convert between watts, kilowatts, horsepower, megawatts and gigawatts.
Force Converter
Convert between newtons, kilonewtons, pounds-force, kilogram-force and dynes.
Torque Converter
Convert between newton-metres, foot-pounds, inch-pounds and kilogram-force metres.
Density Converter
Convert between kg/m³, g/cm³, lb/ft³ and other density units.
Digital, Time & Lifestyle Units
Data storage, transfer rates, time, cooking measurements and shoe sizes.
Time Unit Converter
Convert between seconds, minutes, hours, days, weeks, months and years.
Data Storage Converter
Convert between bytes, kilobytes, megabytes, gigabytes and binary equivalents.
Data Transfer Rate Converter
Convert between bps, Kbps, Mbps, Gbps and related units.
Fuel Economy Converter
Convert between mpg (US), mpg (UK), L/100 km and km/L.
Cooking Measurement Converter
Convert between cups, tablespoons, teaspoons, millilitres and fluid ounces.
Shoe Size Converter
Convert shoe sizes between US, UK, EU and centimetres.
Conversion Guides
Understand the mathematics behind the converters.
Unit Converter FAQs
Length, mass, temperature, area, volume, speed, time, data storage, data transfer rate, pressure, energy, power, force, torque, density, fuel economy, cooking measurements and shoe sizes.
Yes. Conversion factors are defined to the highest practical precision from international standards, including NIST and BIPM references. Values are displayed rounded, but the underlying arithmetic uses full precision.
Where US and UK measurements differ — such as gallons, fluid ounces, miles per gallon and shoe sizes — both variants are available as separate units.
Results are shown with a sensible number of significant digits based on the magnitude of the value. You can adjust decimal precision where the converter allows it — the underlying arithmetic always uses full double-precision.
Explore Other Categories
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