Tools
Unit converter
Convert length, weight, temperature, volume, area, speed and data units.
About this tool
Turning miles into kilometres, pounds into kilograms, Fahrenheit into Celsius or gallons into litres comes up when you follow an American recipe, read a spec sheet, plan a trip or shop from abroad. This converter covers seven categories (length, weight, data, temperature, speed, area and volume) and shows every equivalent at once, so there is no need to pick a from and to unit.
Choose a category from the tabs at the top. A table appears with one row per unit: type the value into the row for the unit you know and the rest recalculate as you type. The row you are typing in is highlighted, and every row has a button to copy its value. Very large or very small numbers switch to scientific notation so they keep their precision.
The maths runs in your browser using fixed conversion factors, and nothing is sent anywhere. In the data category, 1 KB equals 1024 bytes (binary multiples) rather than 1000. For volume, US and UK gallons are listed separately, and pints, cups and fluid ounces are US measures. It does not convert currencies or cooking measures by weight, such as grams of flour to cups.
How do you convert one unit to another?
- Choose the quantity from the tabs at the top: “Length”, “Weight”, “Data”, “Temperature”, “Speed”, “Area” or “Volume”. The page opens on “Length”.
- Find the row for the unit you know and type the value into its box. For example, 5 in the “Mile” row.
- Read the result in the other rows, which recalculate as you type. In the example, the “Kilometre” row shows 8.04672 and the “Metre” row 8046.72.
- Press the copy icon at the end of a row to take its value. If you switch tabs, the table clears and you start again.
Which units does it convert?
“Length”: metre, kilometre, centimetre, millimetre, mile, yard, foot, inch and nautical mile. “Weight”: kilogram, gram, milligram, pound, ounce, stone and tonne.
“Data”: byte, kilobyte, megabyte, gigabyte, terabyte, petabyte, bit, kilobit, megabit and gigabit. “Temperature”: Celsius, Fahrenheit and Kelvin.
“Speed”: metres per second, kilometres per hour, miles per hour, knot and feet per second. “Area”: square metre, square kilometre, square foot, square yard, acre, hectare and square mile.
“Volume”: litre, millilitre, cubic metre, US gallon, UK gallon, and US quart, pint, cup and fluid ounce.
What conversion factors does it use?
Each tab first converts the value to a base unit (metre, kilogram, byte, degree Celsius, metre per second, square metre or litre) and from there to the others. In length the factors are exact by definition: an inch is 2.54 cm, a foot 30.48 cm, a yard 0.9144 m, a mile 1609.344 m and a nautical mile 1852 m.
In weight, area and volume it uses rounded factors, such as 0.453592 kg per pound or 3.78541 litres per US gallon. That is more than precise enough for everyday use; if you work to very fine tolerances, check the official factor.
Temperature is not a simple factor: from Fahrenheit to Celsius you subtract 32 and multiply by 5/9, and to get kelvin you add 273.15 to the degrees Celsius. That is why 0 °C is 32 °F and 273.15 K.
In “Data”, each multiple is 1024 times the previous one (1 KB is 1024 bytes) and a byte is 8 bits. Kilobits, megabits and gigabits follow the same 1024 rule.
How do you read the results?
Each result is shown with up to eight significant figures and a decimal point. If it is smaller than 0.0001 or reaches one billion, it switches to scientific notation with four decimal places: 1.0000e+9 means a 1 followed by nine zeros.
The row you type in is highlighted and keeps what you entered; the others are calculated from it. You can type in any row: the starting value is always the last one you touched.
It accepts negative numbers, which is useful for temperature: -40 °C is -40 °F, the only point where the two scales meet.
Frequently asked questions
How many kilometres are in a mile?
A statute mile is exactly 1.609344 km. The nautical mile, also in the table, is 1.852 km.
How do you convert Fahrenheit to Celsius?
Subtract 32 and multiply by 5/9. For example, 100 °F is about 37.8 °C. The temperature tab does it instantly and shows kelvin as well.
Is a gallon 3.79 or 4.55 litres?
It depends on the country: a US gallon is about 3.785 litres and a UK (imperial) gallon about 4.546. The converter shows both on separate rows.
Why isn’t 1 GB equal to 1000 MB here?
The converter uses binary multiples, as operating systems do: 1 GB is 1024 MB. Drive makers usually use multiples of 1000, which is why a 1 TB drive shows less capacity on your computer.