Online Tool Store
Length Converter
Convert any length between metric and imperial units at once, from micrometres to nautical miles, with your choice of precision. Runs in your browser.
🔒 This tool runs entirely in your browser. Your files are never uploaded to a server.
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Example shown — enter your own value.
All units
| Unit | Value | Copy |
|---|
How it works
- Type a value and pick the unit it is in.
- Choose the unit you want for the headline figure, or just read the full table underneath.
- Use Swap to reverse the pair, and set the decimal places if you need a fixed precision.
- Copy any row's value straight to your clipboard.
One factor per unit, and why that is enough
Converting between eleven units could mean over a hundred conversion factors. It does not, because every unit is defined against the metre and the conversion routes through it:
metres = value × factor(from)
result = metres ÷ factor(to)
So 1.8 m in feet is 1.8 ÷ 0.3048 = 5.9055 ft. One multiply, one divide, and the round trip returns exactly what you started with. Storing a factor per unit rather than a table of pairs is also why adding a unit is a one-line change and cannot introduce an inconsistency between two routes.
The exact definitions
The imperial units here are not rounded approximations of metric ones — since the 1959 international agreement they are defined in metric terms:
1 inch = 25.4 mm exactly 1 foot = 0.3048 m exactly
1 yard = 0.9144 m exactly 1 mile = 1609.344 m exactly
1 nautical mile = 1852 m exactly (one minute of latitude)
Those definitions keep the familiar relationships intact — 12 inches to a foot, 3 feet to a yard, 5280 feet to a mile — while tying the whole system to the metre. The nautical mile is the odd one out: it comes from navigation rather than from feet, which is why it does not divide neatly into any of the others at 1.150779 statute miles.
FAQ
Are the imperial conversions exact or rounded?
Exact. Since 1959 an inch has been defined as precisely 25.4 millimetres, which makes a foot exactly 0.3048 m, a yard exactly 0.9144 m, and a mile exactly 1609.344 m. These are definitions rather than measurements, so there is no approximation to worry about.
Why show every unit at once?
Because the unit you want is often not the one you first picked. Seeing the whole set means you can read off centimetres and inches together when buying a shelf, or metres and yards together on a plan, without converting twice.
What is a thou or mil?
One thousandth of an inch, or 25.4 micrometres. It is standard in engineering and manufacturing for tolerances and material thicknesses — paper, foil, and circuit board layers are usually quoted in thou.
Why is a nautical mile different from a mile?
Because it is defined by the shape of the Earth, not by feet. A nautical mile is exactly 1852 metres — one minute of latitude — which makes it about 1.15 statute miles. Aviation and shipping use it because it maps directly onto navigation charts.
How does the automatic precision work?
It scales with the size of the result: large numbers get two decimals, values around one get four, and small values get six, so a measurement in micrometres stays readable and one in kilometres is not padded with zeros. Fix it to a set number of places if you need consistency.
Is anything I type sent anywhere?
No. All the conversion factors ship with the page and the arithmetic happens in your browser, so nothing is uploaded and it keeps working offline once loaded.
How we compare
| Feature | Online Tool Store | Search engine answer box | Phone calculator |
|---|---|---|---|
| Every unit shown at once | ✓ | One pair at a time | ✗ |
| Chosen precision, not fixed rounding | ✓ | ✗ | ✓ |
| Nothing typed leaves the page | ✓ | ✗ | ✓ |
| Engineering units like thou and micrometre | ✓ | Hit and miss | ✗ |
| Works with no connection | Offline once loaded | ✗ | ✓ |
| Handles feet-and-inches together, like 5′ 11″ | ✗ | ✓ | ✗ |
Useful when you need more than one answer at once — a measurement in centimetres and inches for a supplier, or metres and yards for a plan — with exact factors and precision you control. It takes a single value per conversion, so a compound height like 5′ 11″ needs the inches added up first.