How the Length Converter works
Every unit is stored as an exact fraction of a metre. The imperial units use the international definitions agreed in 1959: one inch is exactly 0.0254 m, one foot is 12 inches (0.3048 m), one yard is 3 feet (0.9144 m) and one mile is 1,760 yards (1,609.344 m). A nautical mile is exactly 1,852 m.
To convert, the tool multiplies your value by the ratio of the two unit definitions, cancelling common factors first so that only one floating point step is involved. Results are then rounded in decimal to the number of significant digits you choose, so you see 2.54 rather than 2.5399999999999996. The feet and inches line rounds the inches first, so it never shows 12 inches.
How to use the Length Converter
- Type a length in the Length box, for example 1.8 or 5280.
- Choose the unit it is in from the From unit list.
- Choose the precision in significant digits.
- Read the table of every unit with its exact definition, and the feet and inches line. Results update as you type.
- Select Copy next to a value to copy it.
Example
Entering 1.8 with Metres (m) selected gives, among others:
Centimetres (cm) 180
Inches (in) 70.86614173
Feet (ft) 5.905511811
Yards (yd) 1.968503937
Feet and inches 5 ft 10.87 inEntering 1 mile gives exactly 1.609344 km, 5,280 ft and 63,360 in.
Common use cases
- Converting heights between metres and feet and inches.
- Converting screen sizes, paper sizes or part dimensions between inches and millimetres.
- Converting running, driving or flight distances between kilometres, miles and nautical miles.
- Checking CSS, CAD or 3D printing measurements that mix metric and imperial units.
Frequently asked questions
How many centimetres are in an inch?
Exactly 2.54. Since 1959 the international inch has been defined as 0.0254 m, so conversions between inches and metric units are exact.
Are the conversion factors exact?
Yes. Every unit is defined exactly in metres: 1 in = 0.0254 m, 1 ft = 0.3048 m, 1 yd = 0.9144 m, 1 mi = 1,609.344 m and 1 nautical mile = 1,852 m. Results are rounded only for display, to the number of significant digits you choose.
What is the difference between a mile and a nautical mile?
A statute mile is 1,609.344 m. A nautical mile, used at sea and in aviation, is 1,852 m, originally based on one minute of latitude.
How is the feet and inches value rounded?
The total length in inches is rounded to two decimal places first and then split into feet and inches, so the result never shows 12 inches. For example, 1.8 m is 5 ft 10.87 in.
Does the converter use the US survey foot?
No. It uses the international foot of exactly 0.3048 m. The slightly different US survey foot was retired for new work at the end of 2022.