How this conversion works
Every unit is defined as an exact multiple of the meter, the SI base unit. To convert, the value is first expressed in meters and then divided by the size of the target unit.
Because the imperial units in common use today are defined in metric terms, conversions such as inches to centimeters are exact, not approximations.
Formula: result = value × (meters per source unit) ÷ (meters per target unit)
Where this conversion is used
- Reading product dimensions: furniture, TVs and phones listed in inches or centimeters.
- Height on forms and medical records (cm vs feet and inches).
- Running and cycling distances in miles or kilometers.
- DIY and machining drawings that mix millimeters with fractional inches.
Worked example: 170 cm to feet and inches
- Convert to inches: 170 ÷ 2.54 = 66.929 in.
- Whole feet: 66.929 ÷ 12 = 5 ft, with 66.929 − 60 = 6.929 in left over.
- Result: about 5 ft 6.9 in.
Unit definitions
| Unit | In meters | Note |
|---|---|---|
| Kilometer (km) | 1,000 | |
| Meter (m) | 1 | SI base unit of length. |
| Centimeter (cm) | 0.01 | |
| Millimeter (mm) | 0.001 | |
| Micrometer (µm) | 0.000001 | |
| Nanometer (nm) | 1e-9 | |
| Mile (mi) | 1,609.344 | International mile = 5,280 ft = 1,609.344 m exactly. |
| Yard (yd) | 0.9144 | International yard = 0.9144 m exactly. |
| Foot (ft) | 0.3048 | International foot = 0.3048 m exactly. |
| Inch (in) | 0.0254 | International inch = 2.54 cm exactly. |
| Nautical mile (nmi) | 1,852 | International nautical mile = 1,852 m exactly. |
Centimeters to inches
| Centimeter (cm) | Inch (in) |
|---|---|
| 1 | 0.3937 |
| 2 | 0.7874 |
| 5 | 1.9685 |
| 10 | 3.937 |
| 15 | 5.9055 |
| 20 | 7.874 |
| 30 | 11.811 |
| 50 | 19.685 |
| 100 | 39.3701 |
Millimeters to inches
| Millimeter (mm) | Inch (in) |
|---|---|
| 1 | 0.0394 |
| 3 | 0.1181 |
| 5 | 0.1969 |
| 6 | 0.2362 |
| 10 | 0.3937 |
| 12 | 0.4724 |
| 19 | 0.748 |
| 25 | 0.9843 |
| 50 | 1.9685 |
Meters to feet
| Meter (m) | Foot (ft) |
|---|---|
| 1 | 3.2808 |
| 2 | 6.5617 |
| 3 | 9.8425 |
| 5 | 16.4042 |
| 10 | 32.8084 |
| 20 | 65.6168 |
| 50 | 164.042 |
| 100 | 328.084 |
Miles to kilometers
| Mile (mi) | Kilometer (km) |
|---|---|
| 1 | 1.6093 |
| 3.1 | 4.989 |
| 5 | 8.0467 |
| 10 | 16.0934 |
| 13.1 | 21.0824 |
| 26.2 | 42.1648 |
| 50 | 80.4672 |
| 100 | 160.9344 |
Precision and sources
Results are calculated from the definitions above and rounded to 12 significant digits; the converter shows up to eight decimal places and the tables four. Reference: NIST Special Publication 811, Guide for the Use of the International System of Units, Appendix B.
Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54 centimeters. The inch has been defined as 25.4 millimeters since the international yard and pound agreement of 1959.
How many feet are in a meter?
One meter is about 3.28084 feet. The exact relationship is defined the other way: one foot is exactly 0.3048 meters.
Is a US mile the same as a UK mile?
Yes. Both use the international mile of 5,280 feet, or exactly 1,609.344 meters. The nautical mile (1,852 m) is a different unit used at sea and in aviation.
What about the US survey foot?
The US survey foot (1200/3937 m) was officially retired at the end of 2022. This converter uses the international foot, which is the standard for everyday and engineering use.