Length Converter

Length Conversion Calculator

Common Length Conversions

Choose a shortcut to set the converter above. It keeps the value you have typed and changes only the units.

• Feet to metres
• Metres to feet
• Inches to centimetres
• Centimetres to inches
• Miles to kilometres
• Kilometres to miles
• Feet to inches
• Inches to feet
• Yards to metres
• Metres to yards

Length Conversion Chart

Values are calculated from the exact definitions of each unit. Inches to centimetres, feet and yards to metres, and miles to kilometres are exact, so those columns are shown in full. Millimetres to inches does not end in a finite decimal, so it is rounded to four decimal places.

How to Convert Length

Every length unit is defined as a fixed fraction or multiple of the metre, so the converter does not need a separate formula for each pair of units. It works in two steps:

1. Convert the value to metres by multiplying by the number of metres in the starting unit.
2. Convert from metres to the target unit by dividing by the number of metres in that unit.

Written as one line: result = value × metres per source unit ÷ metres per target unit. To convert 10 feet to metres, 10 × 0.3048 ÷ 1 = 3.048. To convert 10 feet to inches, 10 × 0.3048 ÷ 0.0254 = 120.

The calculation keeps full precision and rounds only the number you see, so a rounded answer is never used as the starting point for another conversion. Measuring a room, a garden or a trench in feet and need volume? The Cubic Yard Calculator and Concrete Calculator take feet and inches directly, and the Pool Volume Calculator works from your pool dimensions.

Length Conversion Formulas

These relationships are exact definitions. Anything marked as rounded is an approximation of a repeating decimal.

Height Conversion

To convert a height given in feet and inches to centimetres or metres:

1. Multiply the feet by 12 and add the inches to get the total inches.
2. Multiply the total inches by 2.54 to get centimetres.
3. Divide the centimetres by 100 to get metres.

You can also enter the total inches in the converter above. For the reverse, divide centimetres by 2.54 to get inches, then divide by 12 for whole feet and read the remainder as inches.

For example, 5 ft 6 in is 5 × 12 + 6 = 66 inches, and 66 × 2.54 = 167.64 centimetres. These results are exact.

Special Length Units

Some units look alike but are defined differently. The converter labels each one so you can pick the right definition.

Nautical units

The nautical mile is exactly 1,852 metres and is used for sea and air navigation. The fathom, used for water depth, is 6 feet. Here it is 6 international feet, exactly 1.8288 metres.

Surveying units

The chain (66 feet), rod (16.5 feet) and furlong (660 feet) use the international foot, which makes them exactly 20.1168, 5.0292 and 201.168 metres. These are the values NIST gives from 1 January 2023, when it retired the US survey foot. The converter also offers separate legacy versions on the US survey foot, which is 1200/3937 of a metre, about 0.3048006096 metres and slightly longer than the international foot. Use the legacy units only to read older US survey records.

Scientific and astronomical units

The ångström is exactly 10⁻¹⁰ metres and is used for atomic scales. The astronomical unit is exactly 149,597,870,700 metres. The light-year is the distance light travels in a vacuum in one Julian year (365.25 days, or 31,557,600 seconds) at exactly 299,792,458 metres per second, which is exactly 9,460,730,472,580,800 metres. The parsec is defined by IAU 2015 Resolution B2 as exactly 648,000/π astronomical units, about 3.0857 × 10¹⁶ metres. Geometrically it is the distance at which one astronomical unit spans one arcsecond. Working that out with the tangent gives a value about 242 kilometres shorter, so the two agree to 11 significant figures.

Typography units

Print and screen design use several points and picas that are close but not equal. A PostScript point is exactly 1/72 inch, and a pica is 12 points. A TeX point is exactly 1/72.27 inch. The American printer’s point is 0.013837 inch, and its pica is 12 of those points, 0.166044 inch. Use the one that matches your software. PostScript and TeX each define their point exactly within their own system, while the printer’s point is a trade value fixed in inches.

Millimetre values are rounded to 7 decimal places.

The smoot

The smoot is an informal novelty unit, not a standard. This converter uses 67 inches (1.7018 metres), the height of Oliver Smoot. It is included for fun and sits at the end of the list.

Frequently Asked Questions

Sources

• NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically, National Institute of Standards and Technology (inch, foot, yard, mile, nautical mile, ångström, light-year, parsec, and the computer and printer’s point and pica).
• U.S. Survey Foot: Revised Unit Conversion Factors, National Institute of Standards and Technology (chain, rod, furlong and fathom on the international foot, with the legacy US survey values).
• U.S. Survey Foot, National Institute of Standards and Technology (1200/3937 metre and its retirement on 1 January 2023).
• SI base unit: metre, Bureau International des Poids et Mesures (the metre and the speed of light, 299,792,458 m/s).
• IAU Resolutions, International Astronomical Union (2012 Resolution B2: the astronomical unit, 149,597,870,700 m exactly).
• IAU 2015 Resolution B2, International Astronomical Union, arXiv copy (the parsec as exactly 648,000/π astronomical units).
• TeX: The Program (tex.web), Donald Knuth, via CTAN (the TeX point, 7227 pt = 100 in).
• A new unit of measurement to honor an influential MIT alumnus, MIT News (Oliver Smoot’s height of 5 ft 7 in, and the klein as 0.85820896 smoots), and the 1958 bridge measurement, MIT Museum.

The light-year is calculated as the speed of light times one Julian year (31,557,600 seconds). The Smoot is an informal unit with no official standard.