Length converter — feet, inches, metres, miles and more

How to use the length converter

1. Type the distance in Value. Decimals and negative numbers both work.
2. In From, choose the unit you are starting with, such as feet or kilometres.
3. In To, choose the unit you need. The answer appears straight away.
4. Use the swap button between the two lists to reverse the direction.
5. Scroll the table to see the same length in every other unit at once.

What it does and when to use it

The converter handles 13 length units in four families: metric (kilometres down to nanometres), imperial (miles, yards, feet, inches), nautical miles, and two astronomy units (the astronomical unit and the light year). Typical uses are a person’s height on a form that wants centimetres, a race distance in miles, a screen or timber size in inches, or a homework question about the distance to the Sun.

Working out the space a room covers is a different job: square metres and square feet belong in the area converter. For speeds such as km/h and mph, use the speed converter.

How it works

Every unit is stored as a number of metres. The tool converts your value into metres, then divides by the size of the target unit:

result = value × (metres per “from” unit) ÷ (metres per “to” unit)

The key factors are exact by definition:

The light year here is the distance light travels in a Julian year of 365.25 days. The astronomical unit used to be the average Earth–Sun distance and is now a fixed number.

Worked examples

All results below come from the converter itself.

Height. 6 feet = 182.88 centimetres (1.8288 m). Many medical and visa forms ask for height in centimetres, and this is an exact answer because both units are defined from the metre.

Marathon. 42.195 kilometres = 26.2187574565 miles, the familiar “26.2 miles”.

Nautical mile. 1 nautical mile = 1.852 kilometres exactly, which is why a speed of 1 knot equals 1.852 km/h.

Limits and tips

• Feet-and-inches input is not supported. Enter 5 ft 9 in as 69 inches (5 × 12 + 9), or as 5.75 feet.
• Tiny and huge numbers switch to scientific notation in the table, for example 1.222477e-11 astronomical units for 6 feet.
• Parsecs are not included. Professional astronomy tends to use them; 1 parsec is about 3.26 light years.
• To turn running distances into a pace, try the running pace converter. For body mass and parcel weights, the weight converter uses the same exact 1959 definitions.