Length Converter

How to use the length converter

1. Type a number in Value. A decimal point or a decimal comma both work (12.5 or 12,5).
2. Choose the unit you start from in From and the unit you want in To.
3. Read the result as you type. The line below it repeats the full conversion, for example “1 m ≈ 3.2808399 ft”, and Copy puts that line on your clipboard.
4. Press the Swap units button (⇄) to convert in the other direction without retyping anything.
5. Adjust Significant figures if you need more or fewer digits. A “≈” sign tells you that the displayed value has been rounded.

Below the result, the tool lists your value in every unit at once, a quick conversion table for the selected pair (1, 2, 5, 10… up to 1,000), a few common values such as a marathon or an A4 sheet, and the definition of each unit in metres.

Exact definitions used

Every imperial unit in this converter is defined from the metre, and those definitions are exact, not measurements:

• 1 inch = 25.4 mm exactly, fixed by the international yard and pound agreement of 1959.
• 1 foot = 12 inches = 30.48 cm.
• 1 yard = 3 feet = 0.9144 m.
• 1 mile = 1,760 yards = 5,280 feet = 1,609.344 m.
• 1 nautical mile = 1,852 m, the unit used at sea and in aviation, originally close to one minute of latitude.

Because of this, converting 1 mile to metres gives exactly 1,609.344, and 1 foot to centimetres gives exactly 30.48. The inverse direction is usually a repeating decimal: 1 metre is 3.280839895… feet, which is why the result is rounded to the number of significant figures you choose.

Formula for each pair

Every length conversion is a single multiplication. The tool shows the neatest exact form of the factor, for example cm = in × 2.54 or ft = m ÷ 0.3048. Dividing by 0.3048 is exact, while multiplying by 3.28084 is only an approximation, so the division form is preferred when it is the cleaner one. The worked line under the formula applies it to your number.

Precision and rounding

Computers store decimals in binary, which is why a naive calculation can print 0.30000000000000004. This tool rounds every result to the requested number of significant figures (8 by default, up to 12) and removes trailing zeros, so you see 0.3, 2.54 or 1,609.344. Very large or very small results are written in scientific form, such as 5.39957 × 10⁻⁷.

Quick reference

• 1 cm = 0.393701 in; 1 in = 2.54 cm
• 1 m = 3.28084 ft = 1.09361 yd
• 1 km = 0.621371 mi = 0.539957 nautical mile
• 1 mi = 1.609344 km; a marathon (42.195 km) is about 26.2 miles