Length is the conversion people get almost right and then get wrong by a fraction — because the factors everyone remembers are rounded, and rounding compounds. An inch is not about 2.5 cm; it is exactly 25.4 mm, by international agreement since 1959.
What the Length Converter does
Converts between metric, imperial and nautical units using the exact defined factors rather than the approximations. A mile is exactly 1609.344 m, a yard exactly 0.9144 m, a foot exactly 0.3048 m.
Includes nautical miles at exactly 1852 m — a different unit from the statute mile, defined as one minute of latitude, and the reason aviation and shipping speeds are quoted in knots rather than mph.
Open the Length Converter and follow the settings and checks below.
Exact factors, in metres
| Setting | What it means |
|---|---|
| Kilometre | 1000 |
| Mile | 1609.344 — exact by definition |
| Nautical mile | 1852 — exact, one minute of latitude |
| Yard | 0.9144 — exact |
| Foot | 0.3048 — exact |
| Inch | 0.0254 — exactly 25.4 mm |
| Centimetre / millimetre | 0.01 / 0.001 |
| Default conversion | Miles → kilometres |
How to use it
- Enter the value.
- Pick the unit you have and the unit you want.
- Read the result — all other units are shown alongside.
Practical advice
A nautical mile is not a mile. At 1852 m it is about 15% longer than the statute mile, which is why a boat doing 20 knots is moving at roughly 23 mph. Converting the two as though they were the same is a common and occasionally expensive error in navigation and shipping paperwork.
Common questions
Is an inch exactly 2.54 cm?
Yes, exactly — since the 1959 international yard and pound agreement, which defined the inch as precisely 25.4 mm. Before that the US and UK inches differed very slightly, which caused real problems in engineering.
What is a nautical mile for?
It equals one minute of latitude, so it maps directly onto a chart — 60 nautical miles is one degree of latitude. That makes navigation arithmetic trivial, which is why marine and aviation distances use it and speeds are given in knots.
Why not just multiply by 1.6 for miles?
For rough mental arithmetic it is fine. Over a marathon it is out by about 150 m, and in anything engineering or legal the rounding is not acceptable — the exact factor is 1.609344.
Which units are metric here?
Metre, kilometre, centimetre and millimetre. Mile, yard, foot and inch are imperial/US customary, and the nautical mile belongs to neither system.
Useful next tools
- Unit Converter — Length, mass, temperature, area, volume, speed and data.
- Area Converter — Convert acres, hectares, square feet and metres.
- Speed Converter — Convert mph, km/h, m/s, knots and ft/s.
- Weight Converter — Convert kg, pounds, ounces, stone and grams.
- Travel Time Calculator — How long a trip takes from distance and average speed.
- Volume Converter — Convert litres, gallons, cups, pints and millilitres.
Vootkit provides a browser calculator and educational guidance. Results depend on the values and units you enter, so verify important financial, academic, safety or professional decisions with an appropriate authoritative source.
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