Unit Converter

How to Use the Unit Converter

Twelve categories, 81 units, everything calculated in your browser.

How to convert

  1. Pick a category from the first dropdown
  2. Choose the unit you are converting from
  3. Choose the unit you are converting to
  4. Type the value
  5. Press Convert

Speed

The factors are exact by definition. One mile is 1.609344 kilometres and one foot is 0.3048 metres, so 100 km/h is 62.1372 mph and 20 knots is 37.0400 km/h. A knot is a nautical mile per hour, which is why it is not the same as a mile per hour: one knot is 1.852 km/h exactly.

Cooking and recipes

One US cup is 236.588 ml, one tablespoon is 14.7868 ml and one teaspoon is 4.92892 ml, which makes a cup exactly 16 tablespoons and 3 teaspoons. The arithmetic works because the US tablespoon is defined as half a fluid ounce and the cup as 8 fluid ounces. British cups are 284.13 ml, so a recipe written in cups gives a different result depending on where it was written. If a cake comes out wrong, this is usually why.

Pressure

One bar is exactly 100,000 pascals and one standard atmosphere is 101,325 pascals. Since one pound per square inch is 6,894.757 pascals, 1 bar works out at 14.5038 psi, and the 32 psi that car tyres are inflated to is 2.206 bar. Torr and millimetres of mercury are the same thing: both are 133.322 pascals, which is why 760 torr equals one atmosphere.

Is 1 KB 1000 bytes or 1024?

Both answers are right for a different unit. KB, MB and GB are SI units and use base 1000, so 1 KB is 1000 bytes. KiB, MiB and GiB are IEC units and use base 1024, so 1 KiB is 1024 bytes. This converter includes both rather than making you choose.

It explains an everyday puzzle: a drive sold as 1 TB shows as about 931 GB in Windows. The manufacturer counted terabytes as 1,000,000,000,000 bytes and the operating system counts gibibytes, where 1 TiB is 1,099,511,627,776 bytes. Neither is wrong. Marketing picked one and software picked the other.

Energy

One watt-hour is 3,600 joules and one kilowatt-hour is 3.6 million joules. The large calorie used in physics is 4.184 joules, so a kilowatt-hour is about 860 kilocalories. This is where the figure on an electricity bill comes from: the kilowatt-hour is the unit you are billed in, and the kilocalorie is the one on the nutrition label.

Temperature is the exception

Everything else multiplies by a fixed factor. Temperature does not, because there is no single factor between Celsius and Fahrenheit. The scales are offset as well as scaled, which is why 0 °C is 32 °F and not 0. This converter handles it separately instead of pretending a factor exists.

What this tool will not do

It does not convert currencies. Exchange rates change daily, and a rate written into a page would give confidently wrong numbers. Use a bank or a live service for that. Nothing you type here is sent anywhere: the calculation runs in your browser and the page keeps working with the network off.