📏 Length
Length Converter
Convert between metric and imperial units of length — millimetres to miles, and everything in between. Enter a value, choose your units, then press Convert.
About the length converter
Length measures one-dimensional distance. The modern metric system is built on the metre, while everyday life in the United States, the United Kingdom and parts of Canada still relies on inches, feet, yards and miles. This converter bridges the two with exact international definitions, so a result is never an approximation.
Exact conversion factors used
- 1 inch = 25.4 millimetres exactly
- 1 foot = 0.3048 metres exactly
- 1 mile = 1.609344 kilometres exactly
- 1 nautical mile = 1,852 metres exactly
- 1 kilometre = 1,000 metres · 1 centimetre = 10 millimetres
How to convert length
Length measures distance in a single dimension. The SI base unit is the metre, while the imperial system — still used daily in the United States, the United Kingdom and parts of Canada — is built on inches, feet, yards and miles. Every conversion here uses exact international definitions, so results are limited only by the digits shown. That is why 1 inch is 2.54 cm and 1 mile is 1.609344 km with no rounding involved.
Common length conversions
| Unit | 1 meter equals |
|---|---|
| Millimeter (mm) | 1,000 |
| Centimeter (cm) | 100 |
| Inch (in) | 39.370079 |
| Foot (ft) | 3.2808399 |
| Yard (yd) | 1.0936133 |
| Kilometer (km) | 0.001 |
| Mile (mi) | 0.00062137119 |
| Nautical mile (nmi) | 0.0005399568 |
Common height and inch values
| Input | Metric | Also |
|---|---|---|
| 5 foot 7 in | 170.2 cm | 1.702 m |
| 5'7 in cm | 170.2 cm | 1.70 m |
| 5 foot 10 in | 177.8 cm | 1.778 m |
| 175 cm | 5 ft 8.9 in | 68.9 in |
| 175 cm in feet | 5 ft 8.9 in | 1.75 m |
| 5'11 in cm | 180.3 cm | 1.80 m |
| 180 cm in feet and inches | 5 ft 10.9 in | 70.9 in |
| 6 foot 2 in cm | 187.96 cm | 1.8796 m |
| 6'2 in cm | 187.96 cm | 1.88 m |
| 1.8 m in feet | 5 ft 10.9 in | 5.91 ft |
| 3/8 inch | 9.525 mm | 0.375 in |
Common length searches
| Search-style query | What this page can answer | Note |
|---|---|---|
| 1 inch in cm | exactly 2.54 cm | the inch is defined from the centimetre |
| 1 inch in mm | exactly 25.4 mm | millimetres, not the other way around |
| 1 metre in feet | about 3.2808399 ft | 3.28 is a handy rounding, not exact |
| 10 mm to inches | about 0.3937 in | just under four-tenths of an inch |
| 30 cm to inches | about 11.811 in | useful for phone and notebook sizes |
| 100 cm to inches | about 39.37 in | a little over a yard |
Everyday uses
- DIY, carpentry and construction measurements
- Travel distances and route planning
- Clothing, body and furniture measurements
- Screen, paper and photo dimensions
- Science, engineering and astronomy
Frequently asked questions
More worked examples
- A person described as 6 ft 2 in is 1.8796 m tall: 6 × 0.3048 = 1.8288 m, plus 2 × 0.0254 = 0.0508 m.
- A marathon is 42.195 km, which is 26.2188 miles — that is why the classic distance is often loosely called 26.2 miles.
- A 55-inch television measures 139.7 cm across the diagonal (55 × 2.54).
- 100 yards, the length of an American football field between the goal lines, is 91.44 m.
Quick reference
| Conversion | Exact value |
|---|---|
| 1 inch | 2.54 cm |
| 1 foot | 30.48 cm |
| 1 yard | 0.9144 m |
| 1 mile | 1.609344 km |
| 1 metre | 3.2808399 ft |
| 1 kilometre | 0.62137119 mi |
| 1 nautical mile | 1.852 km |
Common mistakes to avoid
- Reading 5'10" as 5.10 feet. It means 5 feet 10 inches, which is 5.8333 ft — a difference of 20 cm.
- Rounding 1 mile to 1.6 km when doing anything precise; the exact factor is 1.609344.
- Confusing the international foot (exactly 0.3048 m) with the US survey foot (1200/3937 m), which is about two parts per million longer and has been phased out for most official use.
- Forgetting that measures such as screen diagonals are quoted in inches while the rest of the specification may be in centimetres.
Further questions
Sources and standards
The metre is defined by the BIPM as the distance light travels in a vacuum in 1/299,792,458 of a second. Every factor on this page derives from that definition or from the exact US customary equivalents in NIST SP 811, where 1 inch is 25.4 mm and 1 foot is 0.3048 m exactly.
- BIPM — The International System of Units (SI Brochure)
- NIST Special Publication 811 — Guide for the Use of the SI
cm to inches, cm to feet and inches to cm
The inch is exactly 2.54 cm, so how many cm in an inch has a precise answer: 2.54. One inch is also 25.4 mm, which answers how many mm in an inch. Going the other way, 1 cm is 0.3937007874 in, and 1 cm is 0.032808399 ft.
| Centimetres | Inches | Feet and inches |
|---|---|---|
| 150 cm | 59.06 in | 4 ft 11.1 in |
| 160 cm | 62.99 in | 5 ft 3.0 in |
| 170 cm | 66.93 in | 5 ft 6.9 in |
| 175 cm | 68.90 in | 5 ft 8.9 in |
| 180 cm | 70.87 in | 5 ft 10.9 in |
| 190 cm | 74.80 in | 6 ft 2.8 in |
Race distances come up in the same searches: 10k in miles is 6.21, marathon in miles is 26.22 (from 42.195 km), and half marathon in km is 21.0975. The dedicated pages are cm to inches, inches to cm and cm to feet.