# Length calculator: convert any unit

Converts a length between millimeters, centimeters, meters, kilometers, inches, feet, yards, miles, nautical miles, and more, with feet and inches.

- Page: https://www.acalculator.org/convert/length
- JSON spec: https://www.acalculator.org/convert/length.json
- Version: 144c3440a331

## Default answer

Example with the default inputs (Length 10, From feet (ft), To meters (m)): 10 feet (ft) = 3.048 meters (m).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| amount | Length | The length to convert, in the "From" unit. |
| from | From | The unit the length is in. |
| to | To | The unit to convert the length to. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| result | Converted length | The length in the "To" unit. |
| meters | Meters (m) | The length in meters. |
| centimeters | Centimeters (cm) | The length in centimeters. |
| kilometers | Kilometers (km) | The length in kilometers. |
| inches | Inches (in) | The length in inches. |
| feet | Feet (ft) | The length in feet. |
| miles | Miles (mi) | The length in miles. |
| feetInches | Feet and inches | Whole feet and the inches left over, to 0.01 in. |

## Method

converted = length × (meters per "From" unit) ÷ (meters per "To" unit)

## Assumptions

- Meters per unit are the exact definitions in NIST SP 811: 1 in = 0.0254 m, 1 ft = 12 in, 1 yd = 3 ft, 1 mi = 5,280 ft, 1 nautical mile = 1,852 m, 1 mil = 0.001 in.
- The arithmetic is exact on the decimal you type; each answer is rounded once, and the page shows at most 6 decimal places.
- Feet and inches round the inches half up to 0.01 in; inches that round to 12 count as one more foot.

## Worked examples

1. amount = 10, from = ft, to = m gives result = 3.048, inches = 120, feetInches = 10 ft 0 in. Source: NIST SP 811 (2008), Appendix B.8: 1 ft = 0.3048 m exactly.
2. amount = 1, from = m, to = in gives result = 39.370079, feet = 3.28084, feetInches = 3 ft 3.37 in. Source: NIST SP 811 (2008), Appendix B.8: 1 in = 0.0254 m exactly.
3. amount = 5, from = km, to = mi gives result = 3.106856, meters = 5,000. Source: NIST SP 811 (2008), Appendix B.8: 1 mi = 1,609.344 m exactly.
4. amount = 1, from = nmi, to = ft gives result = 6,076.115486, meters = 1,852. Source: NIST SP 811 (2008), Appendix B.8: 1 nautical mile = 1,852 m exactly.
5. amount = 178, from = cm, to = ft gives result = 5.839895, feetInches = 5 ft 10.08 in. Source: NIST SP 811 (2008), Appendix B.8: 178 ÷ 2.54 = 70.0787… in = 5 ft 10.08 in.

## FAQ

### How many centimeters are in an inch?

Exactly 2.54. Since 1959 the inch is defined as 0.0254 m (NIST SP 811), so 12 inches are 30.48 cm.

### How many feet are in a meter?

1 m is 1 ÷ 0.3048 = 3.280839895 ft, or 3 ft 3.37 in. A foot is exactly 0.3048 m.

### How many kilometers are in a mile?

A mile is exactly 1.609344 km (5,280 ft). So 5 km is 5 ÷ 1.609344 = 3.106856 miles.

### What is a nautical mile?

A nautical mile is exactly 1,852 m by international agreement, about 6,076.1 ft or 1.15078 statute miles. Ships and aircraft use it, with speed in knots (nautical miles per hour).

### What is a mil?

A mil (also called a thou) is one thousandth of an inch, 0.0254 mm. Machinists and sheet-metal and plastic-film sizes use it. It is not a millimeter.

### How do I turn centimeters into feet and inches?

Divide by 2.54 to get inches, then take whole feet (12 inches each) and keep the rest as inches. 178 cm is 70.08 in, which is 5 ft 10.08 in. The result panel does this for you.

## Sources

- NIST SP 811 (2008), Guide for the Use of the International System of Units, Appendix B.8 (foot, inch, mil, mile, nautical mile, yard), retrieved 2026-10-01. https://www.nist.gov/pml/special-publication-811