17 categories · 232 units

Convert anything.

Type a value and every unit in the category fills in at once. No reload, no upload, no waiting.

Length

25 units

Centimetres to inches, metres to feet, kilometres to miles — and 20 more, from the millimetres on a drawing to the light years in an astronomy paper.
cm → in mm → in ft → m km → mi

Weight and mass

18 units

Kilograms to pounds, grams to ounces, and the stone the UK still weighs people in. Troy ounces are kept separate from ordinary ones.
kg → lb g → oz kg → st g → kg

Temperature

5 units

Celsius, Fahrenheit and kelvin, converted as you type — including the negatives, which is where most converters get the sign wrong.
°C → °F °C → K °F → K

Volume

18 units

Litres to gallons, with the US and imperial gallon listed as the different sizes they actually are — 3.79 L against 4.55 L.
L → gal (US) mL → L fl oz (US) → mL pt (US) → L

Area

12 units

Square feet to square metres, and the two units land is really sold in: the acre and the hectare.
ft² → m² ac → ft² ha → ac ac → m²

Speed

11 units

Kilometres per hour to miles per hour, metres per second to knots, and Mach for the one figure that depends on the air around it.
km/h → mph kn → mph m/s → km/h mph → m/s

Time

14 units

Seconds to minutes, days to hours, years to days. The month and the year are averages here, and the page says which.
h → min d → h min → s wk → d

Data storage

17 units

Megabytes to gigabytes, and the answer to why a 1 TB drive shows up as 931 GB: decimal and binary units are both listed, never mixed.
MB → GB kB → MB GB → TB B → kB

Cooking volume

20 units

Cups to millilitres, tablespoons to teaspoons. A US cup, an imperial cup and a metric cup are three different sizes, and all three are here.
cup (US) → mL tbsp (US) → mL tsp (US) → mL cup (US) → tbsp (US)

Pressure

13 units

PSI to bar and kPa for tyres, millibars for the weather, millimetres of mercury for blood pressure.
psi → bar psi → kPa bar → kPa atm → psi

Energy

16 units

Joules to calories, kilowatt-hours to megajoules. The calorie on a food label is the kilocalorie, and both are listed.
cal → J kJ → kcal kWh → J BTU → J

Power

13 units

Horsepower to kilowatts — with mechanical hp and metric PS kept apart, which is the 10 hp most car figures disagree by.
hp → kW kW → W PS → hp BTU/h → W

Force

12 units

Newtons to pounds-force, kilograms-force to kilonewtons. These are forces, not weights, and the definitions say so.
N → lbf kN → N kgf → N dyn → N

Angle

9 units

Degrees to radians for trigonometry, arcminutes and arcseconds for astronomy and surveying.
° → rad ° → gon ′ → ° turn → °

Frequency

10 units

Megahertz to gigahertz for clocks and radio, RPM and BPM for engines and music.
MHz → GHz kHz → MHz Hz → kHz rpm → Hz

Data transfer rate

12 units

Megabits per second to megabytes per second — the reason a 100 Mbps line downloads at about 12.5 MB/s.
Mbps → MB/s Gbps → Mbps kbps → Mbps

Fuel consumption

7 units

Miles per gallon to litres per 100 km. The two run in opposite directions, and US and UK gallons make two different mpg.
mpg (US) → L/100km mpg (UK) → L/100km km/L → L/100km mpg (US) → km/L

Why this one is faster to use

Every unit at once
Type 5 into centimetres and inches, feet, metres and every other length unit fill in together. Most converters answer one question at a time and reload to answer the next.
Type the unit instead of hunting for it
“5cm to in”, “72f”, “3 miles” — the value box reads all of it and sets the units for you.
Convert a whole column
Paste a column of values from a spreadsheet and copy the converted column straight back. Any row that could not be read is named, never dropped quietly.
Your precision, and the exact value
Choose how many digits you want to see, and copy the full unrounded figure when you need it.