Unit converter

One unit converter for eight kinds of measurement

This unit converter turns one unit into another as you type. It handles length, weight, temperature, volume, area, speed, time and digital data. Use it to check a European clothing size given in centimeters, to follow a recipe written in grams and milliliters, to read a speed limit in km/h on a trip abroad, or to work out how many gigabytes a drive really holds.

Under the result, the tool shows the formula it applied, and a table gives the same value in every unit of that quantity. Everything is calculated in your browser, nothing is uploaded.

How to convert a value

1. On the "Quantity" row, pick Length, Weight, Temperature, Volume, Area, Speed, Time or Data.
2. Type your number in "Value". Decimals and thousands separators are understood: 1,609.344 is read correctly.
3. Choose the starting unit under "From" and the target unit under "To". The ⇄ "Swap units" button exchanges them.
4. Read the "Result", then the "Formula:" line, for example 1 in = 2.54 cm. The "In every unit" table lists the rest, with the target unit highlighted.

Results are rounded to six significant figures. The page address is completed after the # sign: #length:mi:km:26.2 reopens the conversion of 26.2 miles to kilometers, so you can bookmark or share a calculation. Your last choices are also remembered on your device.

The conversions people look up most

For a height in feet and inches, turn everything into inches first: a foot is 12 inches, so 5 ft 7 in is 5 × 12 + 7 = 67 in, which is 170.18 cm or 1.7018 m.

Temperature landmarks

A European recipe that says 180 °C means 356 °F, so set the oven to 350 °F. A recipe at 400 °F is 204.444 °C. The two scales meet at −40: −40 °F is −40 °C.

Mental math shortcuts

• Inches to centimeters: multiply by 2.54. As a quick check, 4 inches is about 10 cm (10.16 cm exactly).
• °F to °C: °C = (°F − 32) ÷ 1.8. Example: (212 − 32) ÷ 1.8 = 100 °C. The other way, °F = °C × 1.8 + 32.
• Miles to kilometers: 1 mile ≈ 1.6 km. A 5-mile run is about 8 km (8.04672 km exactly).
• Kilograms to pounds: 1 kg ≈ 2.2 lb. A 23 kg suitcase allowance is about 50.6 lb (50.7063 lb exactly).

US and UK gallons and pints are not the same

A US gallon is 3.785411784 liters. A UK (imperial) gallon is 4.54609 liters, about 20% more. This is why fuel economy in miles per gallon cannot be compared directly between the two countries. Pints follow the same split: a US pint is 473.176 ml, a UK pint is 568.261 ml. The converter lists all four as separate units, so check where your recipe or figure comes from before choosing.

The cup here is the US customary cup of 236.588 ml, not the 250 ml metric cup used in Australia and Canada. Teaspoons and tablespoons are the metric 5 ml and 15 ml spoons; the US tablespoon is slightly smaller, at about 14.8 ml. The stone, common for body weight in the UK and Ireland, is 14 pounds or 6.35029 kg.

MB versus MiB: why a 1 TB drive shows 931 GB

Drive makers count in powers of 1000: 1 MB is 1,000,000 bytes and 1 GB is 1,000 MB. Some operating systems, Windows among them, count in powers of 1024 while keeping the same letters. Strictly speaking, those binary units are written KiB, MiB and GiB: 1 MiB is 1,048,576 bytes and 1 GiB is 1,073.74 MB. A 1 TB drive therefore holds 931.323 GiB, which Windows displays as "931 GB". No space is missing, only the unit differs.

Frequently asked questions

How many centimeters are in an inch?

Exactly 2.54 cm. The value has been fixed by definition since 1959, it is not a rounded figure. A foot is 30.48 cm and a yard is 91.44 cm.

Are the results exact?

The factors are the official definitions: 0.45359237 kg for the pound, 1,609.344 m for the mile, 1,852 m for the nautical mile. The display is rounded to six significant figures, which is plenty for cooking, DIY or travel. The "Formula:" line gives the factor with more decimals.

What is the difference between a mile and a nautical mile?

A statute mile is 1,609.344 m. A nautical mile, used at sea and in aviation, is 1,852 m. A knot is one nautical mile per hour, or 1.852 km/h.

Can I enter a negative number?

Yes, which matters for temperatures: type -40 or -4. The tool warns you when a temperature is below absolute zero, −273.15 °C or −459.67 °F.