Length converter
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- Formula shown below
- Reviewed
A length converter changes a distance from one unit to another by multiplying through a shared base unit. One inch is exactly 25.4 millimetres by international agreement, so 180 centimetres equals 70.8661 inches, or 5 feet 10.87 inches. One mile is exactly 1,609.344 metres, so 5 kilometres equals 3.106856 miles.
Result
180 cm converted
70.86614173 in
1 cm = 0.3937007874 in
- Conversion factor
- 1 cm = 0.3937007874 in
- Reverse factor
- 1 in = 2.54 cm
- Rounded to 2 decimals
- 70.87 in
180 cm equals 70.86614173 in. The conversion factor is 1 cm = 0.3937007874 in, and the reverse is 1 in = 2.54 cm.
How to use the length converter
- 01
Enter the length
Type the quantity you want to convert. Decimals and very large or small values are all accepted.
- 02
Choose the source unit
Select the unit the number is currently in, from millimetres through to nautical miles.
- 03
Choose the target unit
Select the unit you want the answer in. The result updates as you type, with no submit step.
- 04
Read the factors
The rows beneath the result show the conversion factor in both directions, so the arithmetic can be checked or reused elsewhere.
The formula
result = value × (factor_from ÷ factor_to)
- value
- The quantity being converted.
- factor_from
- Metres per unit of the source unit — 0.0254 for the inch.
- factor_to
- Metres per unit of the target unit.
- result
- The equivalent quantity in the target unit.
Every length unit is defined as an exact multiple of the metre, so conversions route through metres and involve one multiplication and one division. Chaining conversions through intermediate units would introduce avoidable rounding error.
Worked example
- Length
- 180
- From
- Centimetres
- To
- Inches
- Result
- 70.86614 inches
Convert the source quantity to metres: 180 cm × 0.01 = 1.8 m. Divide by the metres-per-inch factor: 1.8 ÷ 0.0254 = 70.86614 inches. Expressed in feet and inches, 70.86614 ÷ 12 = 5 feet with a remainder of 10.87 inches. The reverse factor is exact by definition: one inch equals 2.54 centimetres precisely, not approximately.
Frequently asked questions
How many centimetres are in an inch?
One inch is exactly 2.54 centimetres. This is a definition rather than a measurement: the 1959 international yard and pound agreement fixed the inch at exactly 25.4 millimetres, harmonising slightly different national standards that had existed until then. All inch-to-metric conversions are therefore exact.
How do you convert centimetres to feet and inches?
Divide the centimetre value by 2.54 to obtain total inches, then divide by 12 for whole feet and keep the remainder as inches. For 180 cm: 180 ÷ 2.54 = 70.866 inches, and 70.866 ÷ 12 gives 5 feet with 10.87 inches remaining, so 180 cm is 5 ft 10.9 in.
How many kilometres are in a mile?
One mile is exactly 1.609344 kilometres, and one kilometre is 0.621371 miles. A 5 km race is 3.107 miles, a 10 km race is 6.214 miles, and a marathon of 42.195 km is 26.219 miles. The mile derives from the Roman mille passus, a thousand paces of five feet each.
What is a nautical mile and why does it differ?
A nautical mile is exactly 1,852 metres, or 1.15078 statute miles. It was defined as one minute of arc of latitude along a meridian, which makes chart navigation direct: one minute of latitude is one nautical mile anywhere on Earth. Speed in knots is nautical miles per hour, so 1 knot equals 1.852 km/h.
Why is the metre defined by the speed of light?
Since 1983 the metre has been defined as the distance light travels in a vacuum in 1/299,792,458 of a second. Defining it against a physical constant rather than a platinum-iridium bar means any properly equipped laboratory can realise the standard independently, with far better precision and no risk of the artefact drifting or being damaged.
Which countries still use imperial length units?
The United States, Liberia and Myanmar are the three countries that have not formally adopted the metric system for general use. The United Kingdom and Canada are officially metric but retain imperial units in specific contexts — road distances in miles, personal height in feet and inches, and beer in pints.
Sources
- The International System of Units (SI Brochure) — Bureau International des Poids et Mesures
- International yard and pound agreement of 1959 — US National Institute of Standards and Technology
- NIST Guide to the SI — conversion factors — US National Institute of Standards and Technology
Last reviewed: · Formula and sources verified by Syed Aqeel Ahmad Gillani. See the methodology for how every calculation is derived.