Free length converter. Convert instantly between millimetres, centimetres, metres, kilometres, inches, feet, yards and miles with exact conversion factors.
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Every length converts through metres using exact international definitions: 1 inch is defined as exactly 2.54 cm, 1 foot as 0.3048 m and 1 mile as 1,609.344 m. That makes metric-imperial conversions exact, not approximations.
Every conversion in this tool goes through metres as a common base: result = value × (from-unit in metres ÷ to-unit in metres). The metre factors are exact international definitions, mm: 0.001, cm: 0.01, m: 1, km: 1000, in: 0.0254, ft: 0.3048, yd: 0.9144, mi: 1609.344.
Worked examples: 100 cm to inches is 100 × (0.01 ÷ 0.0254) = 39.3701 in. 5 miles to kilometres is 5 × (1609.344 ÷ 1000) = 8.0467 km. 6 feet to metres is 6 × 0.3048 = 1.8288 m. Going back is free: dividing reverses multiplying, so the same table handles every pair in both directions.
Type a value, choose the unit it is in (From), then choose the unit you want (To). The converted value appears instantly, no page reload, no sign-up. Swap the units to reverse any conversion.
The converter handles decimal values, so 1.5 km, 0.25 mi and 99.9 mm all work. Results are shown to 4 decimal places, more than enough for everyday use, construction and travel planning.
The metric system is the standard for science, engineering and everyday life in almost every country: kilometres for road distances, metres for height and rooms, centimetres for clothing and screens. The United States still uses miles, feet and inches for everyday measurement, and the UK mixes miles for roads with metric for most else.
The two systems are bridged by one exact number agreed internationally in 1959: 1 inch = 2.54 cm. Every other metric-imperial length conversion derives from it, the foot is 12 × 2.54 = 30.48 cm, the yard is 0.9144 m, and the mile is 1,609.344 m exactly.
Centimetres and inches: multiply inches by 2.54 for cm, divide cm by 2.54 for inches. Example: a 34-inch waist is 34 × 2.54 = 86.36 cm; a 180 cm person is 180 ÷ 2.54 = 70.87 in.
Feet and metres: multiply feet by 0.3048, metres by 3.28084. Example: 6 ft = 1.8288 m; 2 m = 6.5617 ft.
Miles and kilometres: multiply miles by 1.609344, km by 0.621371. Example: a 5K race (5 km) is 3.1069 miles; 26.2 miles is 42.165 km.
Heights: 5 ft 7 in = (5 × 12 + 7) = 67 in = 67 × 2.54 = 170.18 cm.
Multiply the From value by the factor to get the To value: inches → cm × 2.54; cm → inches ÷ 2.54; feet → metres × 0.3048; metres → feet × 3.28084; yards → metres × 0.9144; miles → km × 1.609344; km → miles × 0.621371; nautical miles → km × 1.852; millimetres → inches ÷ 25.4.
Handy rules of thumb: miles × 1.6 ≈ km; km × 0.6 ≈ miles; inches × 2.5 ≈ cm; metres × 3.3 ≈ feet. Use the converter above for exact figures.
Entering 5.11 ft for 5 ft 11 in: that is 5 feet 1.3 inches, nearly 10 inches short. 5 ft 11 in is 5 + 11/12 = 5.9167 decimal feet, or 180.34 cm.
Mixing up statute and nautical miles: a nautical mile (1,852 m) is about 15% longer than a road mile (1,609 m). It matters in aviation and sailing, where knots and nautical miles are the working units.
Rounding the metre-to-foot factor to 3.28: that introduces a 0.026% error, 328 ft at 100 m instead of 328.084 ft. Fine for casual use, but use the full 3.28084 factor (as this tool does) for anything you will build or write down.
Exactly 2.54 centimeters. This has been the fixed international standard since 1959, when the US, UK, Australia, Canada, New Zealand and South Africa agreed on it, it is a definition, not a measurement.
1 meter = 3.28084 feet. Since 1 foot is exactly 0.3048 m, the feet-per-meter value is the repeating decimal 1 ÷ 0.3048. For quick mental math, multiply metres by 3.3.
Multiply by 1.609344, the exact factor. Example: 5 miles × 1.609344 = 8.04672 km. A marathon (26.2 miles) is therefore 42.165 km.
Multiply by 0.621371 (or divide by 1.609344). Example: 10 km × 0.621371 = 6.21371 miles.
A nautical mile is exactly 1,852 metres (1.852 km), about 15% longer than a statute mile. It equals one arcminute of latitude, which is why aviation and maritime navigation still use it.
Metric units scale by powers of 10 from a single base unit (the metre), so conversion is just a decimal shift. Imperial units use historical ratios (12 inches to a foot, 3 feet to a yard, 5,280 feet to a mile). The 1959 inch = 2.54 cm definition bridges the two systems.
Convert to total inches first, then multiply by 2.54. For 5'7": (5 × 12) + 7 = 67 inches, and 67 × 2.54 = 170.18 cm. Never enter 5.7 feet, that means 5 feet 8.4 inches.
Exactly 5,280 feet. The chain is: 1 mile = 8 furlongs, 1 furlong = 220 yards, 1 yard = 3 feet, so 8 × 220 × 3 = 5,280.