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Length Converter
Enter a distance, pick the unit you have and the unit you want, and get the result at once, with the same length shown in every other common unit underneath.
Exact definitions behind every factor
Every length unit here is tied to the metre. Since 1983 the metre has been defined as the distance light travels in a vacuum in 1/299,792,458 of a second. The imperial and US units are defined from it too: under the 1959 international yard and pound agreement, 1 yard is exactly 0.9144 metres. Everything else follows by whole-number steps.
- 1 inch = 25.4 mm exactly
- 1 foot = 12 inches = 0.3048 m exactly
- 1 yard = 3 feet = 0.9144 m exactly
- 1 mile = 1,760 yards = 5,280 feet = 1,609.344 m exactly
- 1 nautical mile = 1,852 m exactly (the international value)
Because these are definitions rather than measurements, the converter introduces no error of its own. Only the rounding of the displayed digits differs from the true value.
Quick reference table
| Unit | In metres | Handy equivalent |
|---|---|---|
| 1 inch | 0.0254 | 2.54 cm |
| 1 foot | 0.3048 | 30.48 cm |
| 1 yard | 0.9144 | 91.44 cm |
| 1 mile | 1,609.344 | 1.609344 km |
| 1 nautical mile | 1,852 | about 1.1508 miles |
| 1 kilometre | 1,000 | about 0.6214 miles |
The last two rows are derived: 1,852 ÷ 1,609.344 is about 1.1508, and 1,000 ÷ 1,609.344 is about 0.6214.
Common mistakes with length
- Treating decimal feet as feet and inches. A height of 5.9 ft is 5 ft 10.8 in, not 5 ft 9 in. To convert 5 ft 9 in, change it to inches first (5 × 12 + 9 = 69 in) and then multiply by 2.54 to get 175.26 cm.
- Confusing statute and nautical miles. A nautical mile is about 15% longer than a land mile. Sea and air distances use nautical miles; road signs in miles use the statute mile.
- Mixing up the abbreviations.
mis metre,miis mile,mmis millimetre andMmwould be a megametre. - Rounding before the last step. Convert with full precision and round only the final figure.
Mental shortcuts
For rough work, multiply kilometres by 0.6 to estimate miles, or multiply miles by 1.6 to estimate kilometres. A useful pair to remember is that 5 miles is about 8 kilometres. For small lengths, one inch is a little over 2.5 cm, and one metre is about 3.28 feet, or just over a yard plus three inches.
These shortcuts are fine for estimating a journey or a room, but use the calculator when the number feeds into a purchase, a drawing or a regulation, because small percentage errors add up over long distances.
In practice the converter is used for travel distances, running and cycling routes, room and furniture dimensions, screen and pipe sizes, and checking imported product specifications. When a drawing mixes millimetres with inches, convert everything to one unit before adding anything up.
Worked example
A marathon is commonly quoted as 26.2 miles. How far is that in kilometres?
Inputs
| Value | 26.2 |
|---|---|
| From | Miles (mi) |
| To | Kilometres (km) |
Result
26.2 mi = 42.164813 km
| Micrometres (µm) | 42,164,812,800 |
|---|---|
| Millimetres (mm) | 42,164,812.8 |
| Centimetres (cm) | 4,216,481.28 |
| Metres (m) | 42,164.8128 |
| Inches (in) | 1,660,032 |
| Feet (ft) | 138,336 |
| Yards (yd) | 46,112 |
| Nautical miles (nmi) | 22.767178 |
- Factors are exact definitions where one exists; results are shown to about six significant digits.
Accuracy note: Factors use the standard definitions stated on this page. Results are rounded for display; for engineering or legal work use the full-precision factors.
Frequently asked questions
How many kilometres are in a mile?
One international mile is exactly 1.609344 kilometres. Multiply miles by 1.609344 to get kilometres, or divide kilometres by 1.609344 to get miles.
How many centimetres are in an inch?
There are exactly 2.54 centimetres in one inch, because the inch is defined as 25.4 millimetres.
Is a nautical mile the same as a mile?
No. A nautical mile is exactly 1,852 metres, while a statute mile is 1,609.344 metres. The nautical mile is used in navigation at sea and in the air.
Why does the result show so many decimal places for small values?
Small results keep extra decimals so that they are not rounded to zero. Large results are shown with up to four decimals.
Can I convert feet and inches together?
Convert the total to one unit first. For example, 6 ft 2 in is 74 inches, so choose inches as the source unit and enter 74.
Related calculators
More conversion references
For length conversion tables beyond this tool, see PakMath length conversion tables. PakMath is a sister project of Adzita.