Length unit reference table
Exact meters-equivalents for every unit supported by this converter, per NIST Special Publication 811.
| Unit | Symbol | Meters equivalent |
|---|---|---|
| Millimeter | mm | 0.001 m |
| Centimeter | cm | 0.01 m |
| Meter | m | 1 m |
| Kilometer | km | 1,000 m |
| Inch | in | 0.0254 m |
| Foot | ft | 0.3048 m |
| Yard | yd | 0.9144 m |
| Mile (statute) | mi | 1,609.344 m |
- All imperial figures above are exact defined values under the 1959 international yard-and-pound agreement, not rounded approximations.
- This converter uses statute miles (land miles, 1,609.344 m), not nautical miles (1,852 m), which are used at sea and in aviation.
- The historical US survey foot (≈0.3048006 m) differs from the international foot used here by about 2 parts per million — immaterial for everyday use, but historically significant in US land-survey records.
How are length units defined?
The meter is the SI base unit of length, currently defined by fixing the speed of light in vacuum at exactly 299,792,458 meters per second — a meter is the distance light travels in a vacuum in 1⁄299,792,458 of a second, per the SI Brochure published by the International Bureau of Weights and Measures (BIPM). Metric prefixes (milli-, centi-, kilo-) scale the meter by powers of ten, so a millimeter is 0.001 m and a kilometer is 1,000 m.
Imperial and US customary units of length — the inch, foot, yard and mile — are defined as exact fractions or multiples of the meter under the international yard-and-pound agreement, formalized in 1959 by the national standards bodies of the United States, United Kingdom, Canada, Australia, New Zealand and South Africa. That agreement fixed the yard at exactly 0.9144 m, from which the foot (1⁄3 yard = 0.3048 m), the inch (1⁄36 yard = 0.0254 m) and the statute mile (1,760 yards = 1,609.344 m) all follow exactly. A separate, very slightly different "US survey foot" (about 0.3048006 m) was used in some historical US land-survey work; NIST and the National Geodetic Survey retired it in favor of the international foot, effective at the end of 2022, which is the definition this converter uses throughout.
How to use this length converter
- Enter the length value you want to convert.
- Select the unit that value is currently in, from millimeters up to miles.
- Read the converted results across all six other supported units, shown at once.
- For very large or very small values, check the kilometers or millimeters results, which carry more decimal precision than the rounded feet/yards/miles figures.
The formula behind length conversion
Every input value is first converted to meters using its exact metric or imperial factor, then re-expressed in each of the other units by dividing by that unit's own meters-equivalent. Because all factors are exact defined values rather than measured approximations, converting through meters introduces no additional error.
Common mistakes
- Confusing the statute mile (1,609.344 m, used on land) with the nautical mile (1,852 m, used at sea and in the air) — this converter only handles the statute mile.
- Mixing up metric prefix scales, for example treating centimeters and millimeters as differing by a factor of 100 instead of 10.
- Rounding an intermediate result (such as feet) before converting onward to another unit, which compounds small errors — always convert from the original entered value.
- Assuming the deprecated US survey foot and the standard international foot are identical for high-precision or legal land-survey work — they differ by a tiny but historically significant amount.
Häufig gestellte Fragen
How many meters are in a mile?
One statute mile equals exactly 1,609.344 meters, an exact value fixed under the 1959 international yard-and-pound agreement (1 mile = 1,760 yards, and 1 yard = 0.9144 m exactly). This differs from the nautical mile, which is defined as exactly 1,852 meters.
How do you convert inches to centimeters?
Multiply the number of inches by 2.54, since 1 inch is defined as exactly 25.4 millimeters (2.54 centimeters). For example, 12 inches equals 12 × 2.54 = 30.48 centimeters, which also confirms that 1 foot (12 inches) equals 0.3048 meters.
Is the imperial foot the same everywhere?
The standard "international foot" (0.3048 m exactly) used by this calculator has been the definition adopted by the US, UK, Canada, Australia, New Zealand and South Africa since the 1959 international yard-and-pound agreement. A very slightly different US survey foot existed for historical land-survey purposes, but NIST and the National Geodetic Survey retired it at the end of 2022.
What is the exact meter-to-yard conversion?
One yard equals exactly 0.9144 meters, the defining relationship fixed by the 1959 international yard-and-pound agreement. From this single exact figure, the foot (yard ÷ 3), inch (yard ÷ 36) and mile (yard × 1,760) all follow as exact derived values.
Why does this converter show so many decimal places for some units?
Because the underlying imperial-to-metric factors are exact but not round numbers in the other system (for example 1 mile = 1,609.344 m exactly), converting between systems generally produces a result with several decimal places rather than a tidy whole number, unless the original value happens to be a convenient multiple.
Quellenangaben
- National Institute of Standards and Technology (NIST). Special Publication 811: Guide for the Use of the International System of Units (SI), 2008 Edition.
- International Bureau of Weights and Measures (BIPM). The International System of Units (SI Brochure), 9th edition, 2019 — definition of the meter.
- Astin AV, Karo HA. Refinement of Values for the Yard and the Pound. National Bureau of Standards, 1959 (the international yard-and-pound agreement).
- NIST / National Geodetic Survey. Notice on the retirement of the U.S. survey foot, effective December 31, 2022.