Unit Converter

Convert length, weight, temperature, area, volume, speed, time and data units.

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Convert measurements between metric and imperial

Unit Converter switches a number between units of the same kind: length, weight, temperature, area, volume, speed, time and digital data. Pick a category and two units, and the answer appears as you type.

Every conversion is worked out on your device from a fixed table of conversion factors, so nothing you type is sent anywhere.

How to convert a measurement

Choose a category tab at the top: Length, Weight, Temperature, Area, Volume, Speed, Time or Data.
Pick the unit you’re starting from in the From list and the unit you want in the To list.
Type your number in the From box. The To box and the summary line update instantly.
To work backwards, type in the To box instead — the From box fills in for you.
The swap button between the boxes reverses the direction, using the current result as the new starting value.

Reading the answer and the full table

Summary line: the conversion written out with unit symbols, for example “1 m = 3.2808398950131 ft”.
All conversions: your value in every unit of the category at once, listed under the converter.
Precision: results are kept to 14 significant digits; very large or very small values switch to scientific notation (shown to 7 significant digits), such as 1e-9.
Temperature check: if a temperature falls below absolute zero (−273.15 °C, −459.67 °F or 0 K), a warning says the value isn’t physically possible.

Everyday reasons to convert units

Cooking: turn US cups, tablespoons and fluid ounces from a recipe into millilitres, or an oven setting between °F and °C.
Travel and driving: compare speed limits in km/h and mph, or distances in miles and kilometres.
Home and DIY: change room sizes between square metres and square feet, or lengths between inches and centimetres.
Coursework: check physics and engineering answers across SI and imperial units — it’s one of the picks in our list of online tools for students.

Units that are easy to mix up

Kilobytes vs kibibytes

Drive makers and network speeds use decimal prefixes: a kilobyte (kB) is 1,000 bytes and a gigabyte (GB) is 1,000,000,000 bytes. Many operating systems count in powers of 1,024 instead, which are properly called kibibytes (KiB), mebibytes (MiB) and so on.

The Data category lists both, so you can see the gap: a GiB is about 7% bigger than a GB, and a TiB about 10% bigger.

US and UK gallons, pints and tons

A US gallon is about 3.785 litres, while a UK (imperial) gallon is about 4.546 litres, and pints differ in the same way. Weight has a similar split: the US short ton is 2,000 lb and the UK long ton is 2,240 lb. Each appears separately in the lists, so check which one your source means.

The teaspoon, tablespoon, fluid ounce and cup in the Volume tab are the US measures.

Unit Converter: common questions

How many feet are in a metre?

One metre is about 3.28 feet (3.2808398950131 at the precision shown). The foot is defined as exactly 0.3048 m, so in the other direction one foot is exactly 30.48 cm.

How accurate are the conversions?

The factors use exact legal definitions where they exist — the international yard and pound, and US customary volumes — rather than rounded figures.

Why does a month or a year look odd in the Time category?

Months and years vary in length, so the converter uses Gregorian-calendar averages: a year of 365.2425 days and a month of one twelfth of that, about 30.44 days. For real calendar months between two dates, the Date Calculator is a better fit.

Can it convert currencies?

No. Exchange rates change every working day, so money has its own Currency Converter, which downloads the latest reference rates.

Is anything I enter sent to a server?

No. The unit tables are part of the page and every calculation runs in your browser. More converters are listed under Conversion Tools.