Length Converter
Type a number once — see it in all 8 length units instantly.
Enter a number to see it in every unit.
All units at once
| Unit | Value |
|---|---|
| Micrometer (µm) | — |
| Millimeter (mm) | — |
| Centimeter (cm) | — |
| Meter (m) | — |
| Kilometer (km) | — |
| Inch (in) | — |
| Foot (ft) | — |
| Yard (yd) | — |
| Mile (mi) | — |
| Nautical mile (nmi) | — |
One base unit, eight everyday units
Length conversion is really a single idea applied repeatedly: express every unit in terms of one base unit — the metre — and any conversion becomes multiply-then-divide. This tool converts among eight units, four metric (mm, cm, m, km) and four imperial (inch, foot, yard, mile), and shows all of them at once so you can read across the whole scale from a single input.
The bridge between the two systems has been fixed by international agreement since 1959: one inch is defined as exactly 2.54 centimetres. Every other imperial-to-metric factor follows from that one definition, which is why the conversions here are exact rather than rounded approximations.
The conversion factors
Each unit's value in metres is shown below. To convert, multiply the input by its factor to get metres, then divide by the target unit's factor.
| Unit | Metres per unit |
|---|---|
| Millimetre (mm) | 0.001 |
| Centimetre (cm) | 0.01 |
| Metre (m) | 1 |
| Kilometre (km) | 1000 |
| Inch (in) | 0.0254 |
| Foot (ft) | 0.3048 |
| Yard (yd) | 0.9144 |
| Mile (mi) | 1609.344 |
Worked example 1 — 175 cm to feet and inches
175 cm × 0.01 = 1.75 m. Divide by 0.0254 to get inches: 1.75 ÷ 0.0254 = 68.90 in. That is 5 ft (60 in) with 8.90 in left over, so 175 cm ≈ 5 ft 8.9 in — a handy check when a form asks for height in imperial units.
Worked example 2 — a 10 km run in miles
10 km × 1000 = 10,000 m. Divide by 1609.344: 10,000 ÷ 1609.344 = 6.214 miles. The reverse — a mile in kilometres — is 1609.344 ÷ 1000 = 1.609 km, the number worth memorising for race distances.
Worked example 3 — 6 feet in centimetres
6 ft × 0.3048 = 1.8288 m, and 1.8288 ÷ 0.01 = 182.88 cm. Because the inch is defined as exactly 2.54 cm, this is not an approximation — it is precise to the last digit.
Precision and rounding
- Conversions between metric units (mm ↔ cm ↔ m ↔ km) are just shifts of the decimal point, so they are always exact.
- Imperial-to-metric results can carry long decimals; the tool rounds for display but keeps full precision internally, so chained conversions do not accumulate error.
- The nautical mile (1852 m) and the US survey foot differ slightly from the units here and are used only in specialised navigation and land-survey contexts.
Where each unit shows up
Knowing the natural scale of each unit makes conversions feel intuitive and helps you catch errors. Millimetres measure rainfall and machined parts; centimetres measure body height and paper sizes; metres measure rooms and swimming pools; kilometres measure travel and road signs. On the imperial side, inches measure screens and short lengths, feet measure height and ceilings, yards measure fabric and American-football fields, and miles measure road distance. When a result looks wrong, checking whether the unit suits the thing being measured usually exposes the mistake — a person who comes out as "1.75 mm" tall has clearly picked the wrong row, and should have chosen metres or centimetres instead.
Related conversions
This tool covers straight-line length only. Area (square metres, acres), volume (litres, gallons), weight, and temperature each follow different factors and belong to their own converters. For length, though, the eight units above cover virtually every everyday need — from a screen measured in inches to a road sign posted in kilometres.
Sources & further reading
Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54. One inch equals 2.54 centimeters — an exact value fixed by the 1959 international yard and pound agreement, not a rounded approximation. So 10 in = 25.4 cm and 12 in (1 foot) = 30.48 cm. To convert cm to inches, divide the centimeters by 2.54.
What are the feet, yards and miles to meters conversion factors?
1 foot = 0.3048 m, 1 yard = 0.9144 m, and 1 mile = 1609.344 m (1.609344 km). These all follow from the inch: a foot is 12 inches, a yard is 3 feet, and a mile is 1760 yards. This converter uses these exact factors, so 5 miles = 8.04672 km and 100 m ≈ 328.08 ft.
How precise are the results?
Every conversion keeps up to 10 significant figures, then trailing zeros are trimmed for readability. Very large or very small numbers (roughly 1e15 and above, or below 1e-9) switch to scientific notation, so nothing is silently rounded away to zero. All values come from the exact metric definition of each unit.
Is my input sent to a server?
No. This length converter runs entirely in your browser — the number you type is never uploaded anywhere. The only thing saved is your last chosen unit pair (for example inches → centimeters), kept in your browser's local storage so it is ready next time. The value itself is not stored.
Where can I convert weight, temperature and other units?
This tool focuses on length. For other conversions — weight, temperature, area, volume, speed and data size — visit the Toolhub home, where the matching converters live alongside this one, all free and ad-light.