📏 Length Converter
By ToolNimba Editorial Team · Updated 2026-06-19
Type in any box, every other unit updates instantly.
Switching between metric and imperial length units is a daily hassle, centimetres to inches for a screen, kilometres to miles for a run, metres to feet for a room. This converter handles them all at once: type a value in any unit and every other unit updates instantly, using exact internationally-defined conversion factors so the results are accurate, not rounded guesses.
What is the Length Converter?
The world runs on two families of length units. The metric system, formalised today as the SI (International System of Units), builds everything on the metre, with prefixes for powers of ten: a centimetre is one-hundredth of a metre, a kilometre is a thousand. The imperial and US customary systems use the inch, foot, yard and mile, where the steps are 12, 3 and 1,760 rather than tidy powers of ten. Most countries use metric for everyday measurement; the United States and, for some purposes, the United Kingdom still lean on imperial.
Under the hood every conversion in this tool goes through a single base unit: the metre. Whatever you type is first scaled into metres, then scaled back out to each target unit. That two-step path is why you can mix any units freely, centimetres in, miles out, without a separate formula for each pair. It also keeps the maths consistent: there is exactly one definition of the metre, and every other unit is expressed against it.
The factors are not approximations. Since 1959 the inch has been defined as exactly 2.54 centimetres, which fixes the foot at exactly 0.3048 m, the yard at exactly 0.9144 m and the statute mile at exactly 1,609.344 m. Because these definitions are exact, the only error in a conversion is the precision you choose to round to, the underlying numbers are correct to as many decimals as you need.
When to use it
- Reading screen and TV sizes quoted in inches when you think in centimetres (or vice versa).
- Converting running and cycling distances between kilometres and miles for race planning.
- Working out room and furniture dimensions in metres and feet when reading plans or listings.
- Translating a person’s height between centimetres and feet-and-inches.
- Making sense of travel distances and speed-limit signs abroad in unfamiliar units.
How to use the Length Converter
- Type a number into any unit field.
- Every other unit updates instantly.
- Clear the field to start a new conversion.
Formula & method
Worked examples
Convert 30 cm to inches (e.g. checking a screen width).
- 1 inch is defined as exactly 2.54 cm, so divide by 2.54.
- 30 ÷ 2.54 = 11.811…
Result: 30 cm ≈ 11.81 inches
Convert 5 km to miles (e.g. a Parkrun distance).
- 1 mile = 1.609344 km, so divide kilometres by 1.609344.
- 5 ÷ 1.609344 = 3.10686… (the same as 5 × 0.621371).
Result: 5 km ≈ 3.107 miles
Convert 6 ft to metres (e.g. a person’s height).
- 1 foot = exactly 0.3048 m, so multiply feet by 0.3048.
- 6 × 0.3048 = 1.8288
Result: 6 ft = 1.8288 m ≈ 1.83 m
Exact length conversion factors
| From | Equals |
|---|---|
| 1 inch | 2.54 cm = 0.0254 m |
| 1 foot (12 in) | 30.48 cm = 0.3048 m |
| 1 yard (3 ft) | 0.9144 m |
| 1 mile (1,760 yd) | 1.609344 km = 1,609.344 m |
| 1 centimetre | 0.393701 in |
| 1 metre | 3.28084 ft = 1.09361 yd |
| 1 kilometre | 0.621371 mi |
Common mistakes to avoid
- Confusing statute and nautical miles. A statute mile is 1.609344 km, but a nautical mile (used at sea and in aviation) is 1,852 m, about 15% longer. Make sure you are converting the right kind of mile.
- Rounding 1 inch to 2.5 cm. An inch is exactly 2.54 cm, not 2.5. The 2.5 shortcut drifts by about 1.6%, which adds up fast over longer measurements.
- Multiplying the wrong way. Going from a larger unit to a smaller one (km to miles) the number gets smaller, while metres to feet the number gets larger. Multiply by the factor in one direction; divide in the other.
- Mixing units in a single dimension. Entering one part in feet and another in metres before adding throws the total off. Convert everything to one unit first, then combine.
Glossary
- Metric system
- A decimal system of measurement built on the metre, where units scale by powers of ten (cm, m, km).
- Imperial / US customary
- The system of inches, feet, yards and miles. UK imperial and US customary share length units but differ for some volumes.
- SI base unit
- The metre is the SI base unit of length; every other length unit in this tool is defined as an exact multiple of it.
- Statute mile
- The ordinary land mile of 1,760 yards (1.609344 km), as opposed to the longer nautical mile of 1,852 m.
Frequently asked questions
How many centimetres are in an inch?
Exactly 2.54 centimetres equal one inch, by international definition. So 10 inches is 25.4 cm, and 30 cm is about 11.81 inches.
How do I convert kilometres to miles?
Divide kilometres by 1.609344, or multiply by 0.621371, to get miles. For example, 5 km × 0.621371 ≈ 3.11 miles.
How many feet are in a metre?
One metre is about 3.28084 feet. To go the other way, multiply feet by 0.3048 to get metres, since one foot is exactly 0.3048 m.
How do I convert between metric and imperial length?
Pick the pair you need and apply the exact factor: 1 in = 2.54 cm, 1 ft = 0.3048 m, 1 mi = 1.609344 km. This tool does it for you, type a value in any unit and every other unit updates at once.
Is a yard about the same as a metre?
Almost. One yard is exactly 0.9144 m, so a metre is roughly 9% longer than a yard. They are close enough to estimate by eye, but not interchangeable for precise work.
Are the conversion factors exact?
Yes. The tool uses the internationally-agreed exact factors (for example 1 inch = 0.0254 m), so the only rounding is whatever precision you choose to display.