Unit Converter

Convert length, weight and temperature — mm to inches, kg to pounds, Celsius to Fahrenheit.

This tool runs entirely in your browser. Your data is never uploaded, never stored, and never leaves your device.

Converts length, weight, volume, area and temperature — cm to inches, km to miles, kg to pounds, ml to fluid ounces, Celsius to Fahrenheit — by routing each dimension through a base unit, so any pair inside a dimension works without needing a formula of its own.

How to use it

1Pick a Dimension. Choosing Length, Weight, Volume, Area or Temperature reloads the From and To menus with that dimension's units and resets them to the first two.
2Type a value and set the From and To units; the result appears under Result with the target unit beside it.
3Press the ⇄ button to swap From and To, or copy the figure.

Example

Input: Length · 1 · m → foot
Output: 3.28084

Exact conversions come out exact: a mile in millimetres reads 1609344, not a rounded 1609340. The formatter looks for the shortest rounding that still equals the true value, so definitions that are exact by law — 2.54 cm to the inch, 1.609344 km to the mile, 453.59237 g to the pound — survive, while endless decimals like 39.37007874 in to the metre are rounded rather than invented. Length, weight, volume and area are converted through a base unit; temperature goes via Celsius in both directions.

What happens to your data

The factors are two small constant tables compiled into the page — eight lengths against the metre, seven weights against the gram — so there is no rate service to call and no unit list to fetch. Nothing is written to storage either: reload and the form is back at 1 m → foot with your previous figure gone.

Last updated August 2026

Most unit conversions are looked up once and forgotten: how many cm in an inch, how many km to a mile, what 180°C is in Fahrenheit. This does length, weight, volume, area and temperature in one place, and answers the common ones in writing below so you do not have to touch the tool at all.

The pairs people ask for most — cm to inches and inches to cm, km to miles, feet to metres, kg to pounds, ml to fluid ounces, Celsius to Fahrenheit — all work in both directions, along with every other pair inside a dimension.

A good deal of the trouble with units is not arithmetic but knowing which unit you were given. A US gallon is about 3.79 litres and an imperial gallon about 4.55, a difference of a fifth. A US fluid ounce and a UK fluid ounce differ by about four percent. A US ton is 2,000 pounds, a UK ton 2,240, and a metric tonne 1,000 kilograms. Recipes, shipping documents and older textbooks all move between these without saying which they mean, so the first question is usually whose unit it is, not how to convert it.

How it works

Toolvore routes each dimension through one base unit — metres for length, grams for weight, litres for volume, square metres for area — so any pair works without a formula of its own, and temperature converts via Celsius in both directions, which is why Fahrenheit to Kelvin needs no special case. Results keep exactness where it exists: the formatter looks for the shortest rounding that still equals the true value, so a mile in millimetres reads exactly 1609344 rather than a tidy-looking 1609340 that is four millimetres out. Temperature is the one that behaves differently from the rest, and the reason is worth a sentence: length, weight, volume and area are ratio scales that share a zero, so converting is a single multiplication. Celsius and Fahrenheit do not share a zero, so the conversion needs an offset as well as a factor — which is why a temperature difference converts differently from a temperature. A rise of 10°C is a rise of 18°F, not 50°F.

Common use cases

Converting a recipe between metric and imperial — ml to fluid ounces, grams to ounces, °C to °F
Checking a height or a parcel size given in cm against a limit given in inches
Working out fuel or distance figures given in km when you think in miles
Converting a plot or floor area between square metres, square feet, acres and hectares
Reading a spec written in one system when your tools are calibrated in the other

Frequently asked questions

How many cm are in an inch?＋

Exactly 2.54. The inch has been defined as 2.54 cm by international agreement since 1959, so this is a definition rather than a measurement — which is why the converter returns it without rounding.

How do I convert km to miles?＋

Divide by 1.609344, which is the exact number of kilometres in a mile. So 100 km is 62.1371 miles, and 5 km is 3.10686 miles.

How do I convert Celsius to Fahrenheit?＋

Multiply by 9/5 and add 32. So 180°C is 356°F and 20°C is 68°F. The converter goes the other way with the same formula reversed, and reaches Kelvin through Celsius rather than needing a third rule.

How many ml in a fluid ounce?＋

It depends which fluid ounce. A US fluid ounce is 29.5735295625 ml; an imperial one is 28.4130625 ml — about 4% smaller. Both are listed separately rather than one being quietly chosen for you, because in a recipe the difference is real.

How many feet are in a metre?＋

3.28084, to six figures. Going the other way, feet to meters — spelled either way — is a multiplication by 0.3048 exactly, which is the definition; the reciprocal is an endless decimal, which is why one direction is exact and the other is not.

Is my data sent anywhere?＋

No. Every conversion is a multiplication done in your browser. Nothing is uploaded, nothing is stored, and the tool works with the network off.

Why do two converters give me slightly different answers?＋

Almost always rounding, occasionally definitions. An inch is exactly 2.54 cm and a pound exactly 0.45359237 kg by international agreement, so those cannot disagree — but a converter that rounds to 2.5 or 0.454 will drift, and the drift compounds when a value passes through more than one step. Where the numbers differ by more than a fraction of a percent, the cause is usually a US unit meeting an imperial one rather than an arithmetic error.

How accurate does a conversion need to be?＋

Fewer decimal places than people tend to keep. A converted value cannot be more precise than the one you started with: a recipe that says two cups does not become more exact by being expressed as 473.176 ml. Match the precision of the source — whole millilitres for cooking, one decimal for most measurements, more only when the original was measured to that standard.

What about kilograms and pounds — is that a weight or a mass?＋

Strictly they measure different things: a kilogram is mass, a pound-force is weight, and a pound is used for both depending on context. In every practical setting on Earth the distinction does not change the number, which is why converters treat them as interchangeable. It only starts to matter in physics and engineering, where newtons are used for force precisely to keep the two apart.