Unit Converter
Convert between different units of measurement. Fast, accurate, and easy to use. Supports length, weight, temperature, and more.
Choose a Converter
Select a category to start converting units
Length
Metres, feet, inches, miles and nautical miles, using the exact 1959 inch of 25.4 mm
Mass
Kilograms, pounds, ounces, stone and tonnes for cooking, luggage and body weight
Temperature
Celsius, Fahrenheit and Kelvin readings for ovens, weather, fevers and lab work
Area
Square feet, square metres, acres and hectares for flats, rooms, plots and farmland
Volume
Litres, millilitres, US gallons, cups and cubic feet for cooking, tanks and storage
Time
Milliseconds, seconds, hours, days and weeks up to years, using average months and years
Speed
km/h, mph, m/s, knots and ft/s for driving abroad, running, sailing and flying
Pressure
psi, bar, kPa, atmospheres and mmHg for tyres, weather and blood pressure
Energy
Joules, kWh, kilocalories, BTU and electronvolts for bills, food labels and physics
Frequency
Hertz, kHz, MHz, GHz and THz for radio stations, audio, monitor refresh rates and CPUs
Digital Storage
Bytes, KB, MB, GB and TB alongside binary KiB, MiB and GiB, so drive sizes finally add up
Fuel Economy
mpg (US and UK), L/100km and km/L, including the inverse maths that trips people up
Plane Angle
Degrees, radians, gradians, arcminutes and milliradians for code, maps and surveying
Data Transfer Rate
Mbps to MB/s and back, so internet plan speeds match what your downloads show
Common conversions at a glance
The ones people look up most often.
1 inch
= 2.54 cm
1 kg
= 2.205 lbs
1 mile
= 1.609 km
0°C
= 32°F
1 gallon (US)
= 3.785 liters
1 foot
= 30.48 cm
100 km/h
= 62.1 mph
1 GB
= 1,024 MB
Which converter should you open?
Each unit type has its own page with a reference table, worked examples and the mistakes specific to it. Length, mass, temperature and volume cover most everyday questions. Area and volume are the ones to double-check, because squaring and cubing the length factor is where hand calculations go wrong.
Digital storage and data transfer rate are the converters people need when numbers on a box don't match what a computer shows: a "1 TB" drive appearing as 931 GB, or a 100 Mbps plan downloading at 12 MB/s. Fuel economy handles the inverse maths between mpg and L/100km.
Most factors are exact by definition (an inch is exactly 25.4 mm, a pound exactly 0.45359237 kg), so results are only rounded for display. The exceptions are time, where months and years are averages, and anything involving US versus UK gallons.
How the conversions are done
Each category has a base unit, such as the metre for length or the kilogram for mass, and every unit is stored as an exact factor of it. A conversion multiplies into the base unit and divides out to the target, so going from inches to centimetres is 1 inch × 0.0254 ÷ 0.01 = 2.54 cm. Temperature and fuel economy are the exceptions, since they need offsets or inverse formulas rather than a single factor.
| Definition | Exact value | Source |
|---|---|---|
| 1 inch | 25.4 mm | International yard and pound agreement, 1959 |
| 1 pound | 0.45359237 kg | Same agreement |
| 1 US gallon | 3.785411784 litres | 231 cubic inches |
| 1 nautical mile | 1,852 m | International definition |
| 1 calorie (thermochemical) | 4.184 J | Definition |
| 0 °C | 273.15 K | Kelvin scale definition |
Results are shown to up to 8 decimal places, with trailing zeros removed, and very small results below 0.000001 switch to scientific notation. That's far more precision than a measurement usually has, so round the answer to match your input: a length measured to the nearest centimetre doesn't need its conversion quoted to the micrometre.
Limits worth knowing
- One value at a time. Mixed units such as 5 ft 9 in need converting to one unit first (69 inches).
- US customary volumes only: imperial pints and gallons aren't listed, so divide by 0.568 for UK pints or by 4.546 for UK gallons.
- Cooking conversions between volume and weight, such as cups of flour to grams, need the ingredient's density and aren't covered.
- Currency isn't a unit conversion here, since rates change daily; use the Currency Converter.