Length Converter

How Length Converter works

Convert length between millimetres, centimetres, metres, kilometres, inches, feet, yards and miles instantly. Everything happens inside this page: the tool reads your input, runs the calculation or conversion locally, and hands the result back to you. Nothing is transmitted, because there is no backend to transmit it to.

That design choice is deliberate. Most free tool sites upload your files to a server, process them there, and quietly keep a copy. Toolcin cannot do that — the site is a set of static files. If your connection dropped the moment the page finished loading, every tool would still work.

Nine length units, one base

Every unit here is defined as a multiple of the metre, so converting is two multiplications: value × factor of the source unit, then divide by the factor of the target. Typing a value in metres fills in every other unit at once.

Two of the nine are not SI: the inch and its descendants are defined from the metre (1 in = 0.0254 m exactly), and the nautical mile is defined as 1,852 m — one minute of latitude on the reference ellipsoid, not a statute mile.

The one that catches people out

mi and nmi look similar and are not. A statute mile is 1,609 m and a nautical mile is 1,852 m — a 15% difference. Using the wrong one on a flight plan or a sea chart is not a rounding error, it is a different journey.

Similarly, in and ft: twelve inches to a foot, and the decimal feet shown here are not the same as feet-and-inches notation. 5.5 ft is 5 ft 6 in, not 5 ft 5 in.

Precision where it matters

The factors are exact definitions, so the only rounding is in the display. At building scale, a millimetre either way is invisible; at survey scale, four decimal places on a mile still leave a centimetre of uncertainty — and that is a limit of the input, not the conversion.

Clicking any result copies it, which is faster than reading six digits off the screen.

Good to know

• Works offline once loaded, including on flights and in locked-down networks.
• No file size limit beyond your device's own memory.
• Free to use, with no account and no usage counter.
• Results are produced locally, so they are not logged or shared with anyone.

Questions