Length Converter

Every length is converted through the metre. Your value is multiplied by its unit's factor to reach metres, then divided by the target unit's factor. One pass, no accumulated rounding.

The factors are the exact defined values, not approximations. An inch is not roughly 2.54 centimetres — since the international yard agreement of 1959 it is defined as exactly 0.0254 metres. A mile is exactly 1609.344 m. Using 2.5 or 1.6, as rough mental conversions do, introduces an error of about 2% that compounds over a long distance.

The nautical mile is the odd one out. At exactly 1852 metres it was defined as one minute of latitude along a meridian, which is why it survives in aviation and shipping where position is measured in degrees rather than in kilometres.

Results are shown for every unit at once rather than making you pick a target. The usual two-dropdown design answers one question and then makes you re-pick to answer the next.

You are buying a rug listed as 5'3" × 7'10" from a US site, and your room is measured in centimetres.

5 feet 3 inches is 63 inches. Type 63, choose inches, and read 160.02 cm. The other dimension, 94 inches, comes out at 238.76 cm. So the rug is roughly 160 × 239 cm — which you can now hold against a room you measured with a metric tape.

A second case where the exactness matters. A marathon is 42,195 metres. Type that, choose metres, and the answer is 26.2188 miles — the famous “26.2”. Convert with the rough factor of 1.6 km per mile instead and you get 26.37 miles, an error of nearly 300 metres. Over a race distance that is the difference between a personal best and a mis-measured course.

One thing the tool will not do for you: feet-and-inches notation. Convert 5'3" to 63 inches yourself first — the tool takes a single number, because guessing at mixed-unit notation is how converters produce confidently wrong answers.

For land and floor plans rather than lengths, the area converter handles square metres, dunams and acres.