About Length Converter
Length Converter changes a distance from one unit to another across nine choices — millimetres, centimetres, metres, kilometres, inches, feet, yards, miles and nautical miles. Enter a value, pick the unit it is in, pick the unit you want, and it returns the converted figure.
The conversion runs through a common base unit using the exact international definitions: an inch is defined as precisely 25.4 millimetres, a foot as 0.3048 metres, a mile as 1609.344 metres and a nautical mile as exactly 1852 metres. Because those relationships are fixed by definition rather than measured, conversions in either direction stay consistent and reproducible, which matters when a value has to be handed between metric and imperial systems.
The output is a bare number rounded to eight decimal places, and the unit it represents is the one you chose in the second selector — there is no trailing label to read off. For very large or very small results the figure can be long, so round it to the precision you actually need after copying it.
The nine units are the whole set, and nothing outside it can be reached by typing. There is no astronomic unit, light year, parsec, fathom or survey foot, and no way to add a custom unit or factor of your own — a niche unit has to be converted by hand or with a conversion factor applied separately. The result is a plain decimal figure only: scientific notation is not available for very small or very large magnitudes, nor are fractions for the imperial units in the form a tradesperson might expect. A table of all nine equivalents at once is not produced either, so converting one value into several units means repeating the operation, and no formula or working is shown to check the arithmetic against.
How to use Length Converter
- 1 Enter the distance you want to convert.
- 2 Choose the unit the distance is currently in from the From list.
- 3 Choose the unit you need from the To list, then run the tool to see the result.
Frequently asked questions
Are the conversion factors exact?
Most are, by international definition. An inch is exactly 25.4 millimetres, a foot exactly 0.3048 metres and a nautical mile exactly 1852 metres. Because the factors are fixed constants rather than measurements, repeated conversions give consistent results.
Why is the result just a number with no unit after it?
The output shows the converted figure alone; the unit you selected in the To list tells you what it means. Keeping the result as a plain number makes it easy to paste into a spreadsheet or a further calculation.
How precise is the answer?
It is rounded to eight decimal places. That is far more precision than any physical measurement justifies, so for display purposes you will usually want to round to two or three significant digits.
Is a nautical mile the same as a regular mile?
No, and the difference is substantial. A nautical mile is defined as exactly 1852 metres, while a statute mile is 1609.344 metres, so a nautical mile is roughly 15 percent longer. Nautical miles are used in aviation and marine navigation because they correspond closely to one minute of latitude.
Free, online, and private
Free to use
Length Converter is completely free. There is no account to create, no login, and no hidden charge or usage limit.
Runs online in your browser
It is a free online tool that runs entirely in your browser. Nothing to download or install — open the page and start using it right away.
Your data stays private
All processing happens locally on your device. Your input is never uploaded, stored, or tracked, so it never leaves your browser.
How Length Converter behaves in detail
These are the specifics of this implementation — the exact ranges, defaults and fixed settings you are working with.
| Parameter | Value |
|---|---|
| Units covered | 9 — mm, cm, m, km, in, ft, yd, mi and nautical miles |
| Conversion basis | metre |
| Anchors | 1 in = 0.0254 m · 1 ft = 0.3048 m · 1 yd = 0.9144 m · 1 mi = 1,609.344 m |
| Nautical mile | fixed at 1,852 m — the modern international definition |
| Result precision | 8 decimal places, from a starting Value of 1 |
| Default pair | m → ft |
Compiled from the implementation of this tool and checked against it by itoolnet.
What Length Converter does not do
Knowing the edges of a tool saves more time than another list of its features. These are the cases where it will not do what you might expect.
- The factors are the international definitions: yard 0.9144 m, foot 0.3048 m. If your source uses US survey feet at 0.3048006096 m or survey miles, the roughly 2-parts-per-million difference will not show up anywhere in the answer.
- Small results are printed in exponential notation. Rounding to eight decimals leaves one millimetre as 6.2e-7 miles, because the number is converted to a string and JavaScript switches to exponent form below 1e-6 — fine in code, awkward inside a document.
- Everything outside the nine units is a two-step job. Furlongs, chains, rods, fathoms, ångström, light-years and parsecs are all missing, so a value given in any of them has to be moved through metres by hand before this converter becomes usable.
Tested and documented by itoolnet, the team that builds and maintains this site.