Unit Converter — length, weight, temperature, volume

How to use

What it's for

Change a measurement from one unit to another — metres to feet, kilograms to pounds, Celsius to Fahrenheit, square metres to square feet — for a recipe, a floor plan, a parcel or a weather report.

Before you start

Have the number, and know the unit it is in and the unit you want, such as 25 °C into Fahrenheit or 2 litres into cups.

Choose what you are measuring
Tap one of the buttons along the top: Length, Weight, Temperature, Area, Volume, Speed or Time. The unit menus change to match and start on a common pair.
Type the number
Type it in Amount as a plain number, such as 1500 or 2.5 — no commas and no unit.
Choose the two units
In From, pick the unit your number is in; in To, pick the unit you want. Swap turns the two around, for going back the other way.
Convert
Press Convert to bring the answer into view — it also updates as you type, so you can try several numbers in a row.

Reading the result

The big figure is your amount in the To unit, with what you are measuring and that unit's name above it, and what you typed under it.
In: the same amount in the standard unit for that kind of measure, such as metres for length — a handy check.
Rate: how much one of your unit is worth in the other, such as 1 m = 3.2808 ft. Temperature shows no rate, because it is not a simple multiplication.
A line under the inputs warns about each kind where it matters, such as the gallons under Volume being US gallons.

If it goes wrong

It says Enter a number to convert.: the amount is empty, or it has a comma or a unit typed in it. Type 1500, not 1,500 or 1500 g.
Gallons look about a fifth off: the gallons here are US gallons, and a recipe or fuel figure from the UK uses the larger imperial gallon.
There are no months or years under Time: they are not a fixed length, so no single number converts them. Use the Date Calculator to count spans on the calendar.

What this is

Seven categories — length, weight, temperature, area, volume, speed and time — with the units people reach for rather than every unit that exists.

Each conversion goes through one base unit: your figure is converted into metres, kilograms or kelvin, then out again into whatever you asked for. That means adding a unit can never break an existing pair, and the two directions always agree with each other.

Questions

Why is 20 °C not 36 °F?

Because temperature scales have an offset, not just a different step size. Fahrenheit starts 32 degrees below Celsius, so you multiply by 9/5 and then add 32 — 20 °C is 68 °F. Multiplying alone is the single most common conversion mistake, which is why this tool does not quote a rate for temperature.

Are the gallons US or imperial?

US. A US gallon is 3.785 litres; an imperial gallon is 4.546 litres, about 20% larger. Recipes and fuel figures from the UK use the imperial one, so a number that looks a fifth out is usually this.

Why can I not convert months or years?

They are not fixed durations. A month is 28 to 31 days and a year is 365 or 366, so any single factor would be wrong most of the time. Use the Date Calculator, which counts the actual calendar.

Are the figures exact?

The definitions are. An inch is exactly 0.0254 metres and a pound is exactly 0.45359237 kilograms by international agreement, so nothing is approximated on the way in. Only the displayed result is rounded, to about eight significant figures.

How it converts

Everything routes through a base unit

your unit base target unit

Temperature is different

20 °C to Fahrenheit

20 × 9/5 36

then + 32 68 °F

Every other category is a plain multiplication. Temperature has an offset, so stopping at 36 would be wrong by 32 degrees.

Exact by definition

1 inch 0.0254 m

1 pound 0.45359237 kg