Length Converter

Length Converter handles every unit of distance that comes up in practice, from nanometres to light years, and shows them all at once rather than one conversion at a time. Enter a measurement in any unit and the whole family appears.

The factors are the exact defined ones. An inch has been exactly 25.4 millimetres by international agreement since 1959, a yard exactly 0.9144 metres and a mile exactly 1609.344 metres. Those are definitions, not measurements, so the conversion is exact and the twelve-digit figure is meaningful rather than noise.

The nautical mile is the one that catches people out: it is 1852 metres exactly, not 1609, because it was defined as one minute of latitude. That is a fourteen per cent difference, which matters a great deal in aviation and at sea, and it is why a knot is not a mile per hour.

The page shows its working, not just its answer. Where there is a formula it is printed with your own numbers substituted in, so you can check the result rather than take it on trust -- which is the difference between a calculator you can use for something that matters and one you cannot.

Everything runs inside your browser. What you type is never uploaded, never logged and never stored, and the calculator keeps working if your connection drops after the page has loaded.

• Shows result, to twelve digits, conversion factor, the other way and in scientific notation together, so you are not running it twice
• A results table you can read across
• Updates as you type, with no button to press and no page reload
• Copy the result in one click
• Free, no sign-up, and it runs entirely in your browser

The length converter is used by writers, developers, students, marketers and anyone else who needs the job done once without installing software. Common cases include:

• Converting centimetres to inches for a measurement
• Working out a height in feet and inches from metres
• Converting a distance between miles and kilometres
• Checking a specification given in millimetres