Length Converter
Metric & Imperial · 10 units
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Length Quick Reference
One inch is exactly 2.54 centimeters, one foot is exactly 0.3048 meters and one mile is exactly 1.609344 kilometers. These values have been fixed by international agreement since 1959, so they are definitions, not rounded measurements. Enter a value above, pick the two units, and the converter shows the result in all ten length units at once.
The most common length conversions, exact values per international definitions.
| From | To | Multiply by |
|---|---|---|
| inches | centimeters | 2.54 (exact) |
| feet | meters | 0.3048 (exact) |
| miles | kilometers | 1.609344 (exact) |
| yards | meters | 0.9144 (exact) |
| kilometers | miles | 0.62137 |
| meters | feet | 3.28084 |
| cm | inches | 0.393701 |
All metric prefixes follow powers of 10: 1 km = 1,000 m = 100,000 cm = 1,000,000 mm. Imperial units use irregular ratios: 12 inches = 1 foot, 3 feet = 1 yard, 1,760 yards = 1 mile.
Inches to Centimeters and Millimeters
US tape measures mark fractions of an inch. Because 1 inch is exactly 25.4 mm, every value below is exact, not rounded.
| Inches | Centimeters | Millimeters |
|---|---|---|
| 1/16 in | 0.15875 | 1.5875 |
| 1/8 in | 0.3175 | 3.175 |
| 1/4 in | 0.635 | 6.35 |
| 3/8 in | 0.9525 | 9.525 |
| 1/2 in | 1.27 | 12.7 |
| 5/8 in | 1.5875 | 15.875 |
| 3/4 in | 1.905 | 19.05 |
| 1 in | 2.54 | 25.4 |
| 2 in | 5.08 | 50.8 |
| 3 in | 7.62 | 76.2 |
| 6 in | 15.24 | 152.4 |
| 12 in (1 ft) | 30.48 | 304.8 |
A quick check for the workshop: 1/4 inch is just over 6 mm, and 4 inches is just over 10 cm (10.16 cm).
Height in Feet and Inches to Centimeters
Turn the height into inches first (feet × 12 + inches), then multiply by 2.54. Values rounded to one decimal.
| Height | Total inches | Centimeters |
|---|---|---|
| 4 ft 10 in | 58 | 147.3 |
| 5 ft 0 in | 60 | 152.4 |
| 5 ft 2 in | 62 | 157.5 |
| 5 ft 4 in | 64 | 162.6 |
| 5 ft 6 in | 66 | 167.6 |
| 5 ft 8 in | 68 | 172.7 |
| 5 ft 10 in | 70 | 177.8 |
| 6 ft 0 in | 72 | 182.9 |
| 6 ft 2 in | 74 | 188.0 |
| 6 ft 4 in | 76 | 193.0 |
Going the other way, divide centimeters by 2.54 to get inches, then divide by 12. The whole number is feet and the remainder is inches: 170 cm is 66.93 inches, or 5 ft 6.9 in.
Race and Road Distances in Miles and Kilometers
| Distance | Kilometers | Miles |
|---|---|---|
| 1 mile | 1.609 | 1 |
| 5K | 5 | 3.107 |
| 10K | 10 | 6.214 |
| 15K | 15 | 9.321 |
| 10 miles | 16.093 | 10 |
| Half marathon | 21.0975 | 13.109 |
| Marathon | 42.195 | 26.219 |
| 50K | 50 | 31.069 |
| 100K | 100 | 62.137 |
Speed limits convert with the same factor: 55 mph is 88.5 km/h and 100 km/h is 62.1 mph. For other speed units, use the speed converter.
Length Conversion Mistakes to Avoid
- Reading decimal feet as feet and inches. 5.5 ft is 5 ft 6 in (167.64 cm), not 5 ft 5 in (165.1 cm). Multiply the decimal part by 12 to get inches.
- Rounding the factor too early. With 3.28 feet per meter, 1,000 m comes out as 3,280 ft instead of 3,280.84 ft. Keep the full factor and round the answer.
- Mixing up nautical and statute miles. A nautical mile is exactly 1,852 m, about 1.1508 ordinary miles. Charts for boats and aircraft use it; road maps do not.
- Old survey records. Many older US land surveys use the US survey foot (1200/3937 m), which is 2 parts per million longer than the international foot. Over a mile that is only about 3.2 mm, but it matters for property boundaries and state plane coordinates. It was retired for federal use at the end of 2022.
Method and sources. Factors from NIST Special Publication 811 (Appendix B) and NIST Handbook 44 (Appendix C): 1 in = 2.54 cm, 1 ft = 0.3048 m, 1 yd = 0.9144 m and 1 mi = 1,609.344 m exactly, all from the 1959 international yard and pound agreement; 1 nautical mile = 1,852 m exactly. The light year follows the IAU definition (speed of light times a Julian year of 365.25 days), 9,460,730,472,580,800 m. US survey foot: NIST and NOAA Federal Register notice of 2020, effective 1 January 2023. Every table value was computed from these exact factors.
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Length Conversion Questions
One inch equals exactly 2.54 centimeters, by international definition since 1959. This is an exact value, not an approximation. To convert inches to cm, multiply by 2.54. To convert cm to inches, divide by 2.54 (or multiply by 0.393701). Example: 6 inches = 15.24 cm. 30 cm = 11.811 inches.
One meter equals about 3.28084 feet (exactly 100/30.48 feet). One foot equals exactly 0.3048 meters; that value is fixed by international agreement. Common conversions: 5 feet = 1.524 m · 6 feet = 1.8288 m · 1.80 m = 5 feet 10.87 inches. For height conversion, use feet and inches separately.
One international mile equals exactly 1.609344 kilometers. Conversely, 1 km = 0.621371 miles. Common running distances: 5 km = 3.107 miles · 10 km = 6.214 miles · 21.097 km (half marathon) = 13.109 miles · 42.195 km (marathon) = 26.219 miles. Speed signs in the UK show mph; in mainland Europe they show km/h.
There are exactly 12 inches in one foot. The foot is divided into 12 inches, and each inch is divided into fractions (typically halves, quarters, eighths and sixteenths in construction). Other imperial length relationships: 3 feet = 1 yard · 5,280 feet = 1 mile · 1,760 yards = 1 mile. One foot = 30.48 cm = 0.3048 m.
Divide centimeters by 30.48 to get total feet as a decimal. Subtract the whole number of feet to get the fractional part, then multiply by 12 to get inches. Example: 175 cm ÷ 30.48 = 5.7415 feet = 5 feet 8.9 inches. Common heights: 160 cm = 5’3” · 170 cm = 5’7” · 180 cm = 5’11” · 190 cm = 6’3”.
A nautical mile equals 1,852 meters (1.852 km), which is approximately 1.151 international miles. It was originally based on one minute of arc of latitude along a meridian, and since 1929 it has been defined as exactly 1,852 meters. Nautical miles are used in aviation and maritime navigation because they correspond directly to degrees of latitude. One knot = one nautical mile per hour.
One inch equals exactly 25.4 millimeters (since 1 inch = 2.54 cm = 25.4 mm). This is the standard used in engineering and manufacturing. Common conversions: 10 mm = 0.3937 in · 25 mm = 0.984 in · 100 mm = 3.937 in. Wrench and bolt sizes are measured in mm (metric) or fractions of inches (imperial), which is why both systems still coexist in manufacturing.
One light year is approximately 9.461 × 10¹&sup5; meters (9.461 trillion km or about 5.879 trillion miles). It is the distance light travels in a vacuum in one Julian year (365.25 days). The nearest star system, Alpha Centauri, is about 4.37 light years away. Light years are used only for astronomical distances: they are not practical for everyday measurement.
One yard equals exactly 0.9144 meters, so a meter is slightly longer than a yard (by 8.56 cm, or about 3.37 inches). One yard = 3 feet = 36 inches. Yards are used in American football (field = 100 yards), fabric measurement in the US/UK, and golf (distances to the hole). Meters are used for the same purposes in most of the rest of the world.
A quick mental trick: multiply miles by 1.6 to get an approximate km value. Multiplying by 8 and dividing by 5 gives the same result without decimals. Example: 60 miles × 1.6 = 96 km (exact: 96.56 km). Going the other way, multiply km by 0.6 to get approximate miles. The Fibonacci sequence also works: consecutive Fibonacci numbers (5, 8, 13, 21, 34...) approximate the miles-to-km ratio.
A mile is exactly 1,609.344 meters, which is 5,280 feet or 1,760 yards. That is why the 1,600 m race on a track is a little short of a mile: 1,600 m is 0.994 miles, 9.344 m less than a full mile.
One meter is about 39.37 inches (39.3700787 in, exactly 100 ÷ 2.54). In feet and inches that is 3 ft 3.37 in, so a meter is a bit more than a yard, which is 36 inches.
Not for new federal work. Since 1 January 2023 NIST and NOAA use only the international foot, exactly 0.3048 m. The US survey foot (1200/3937 m, about 0.3048006 m) still appears in older deeds and survey records. The two differ by 2 parts per million, about 3.2 mm over a mile.