Enter any length — in millimetres, centimetres, metres, kilometres, inches, feet, yards or miles — and see it converted into every other unit at once.
What Is a Length Converter?
A length converter changes a measurement from one unit to another — metric units (millimetres, centimetres, metres, kilometres) and imperial/US units (inches, feet, yards, miles). All conversions run through metres, the international standard unit of length, using exact defined factors: 1 inch is exactly 2.54 cm, 1 foot is exactly 0.3048 m, and 1 mile is exactly 1.609344 km. This converter shows your value in all eight units at once, so you never need a second lookup.
How to Use
- Enter the value you want to convert.
- Choose the unit it is measured in.
- Click “Convert Length”.
- Read the same length in all eight units.
Formula
Convert to metres first (value × the unit’s factor in metres), then divide by the target unit’s factor. Factors: mm 0.001, cm 0.01, m 1, km 1000, inch 0.0254, foot 0.3048, yard 0.9144, mile 1609.344.
Worked Example
100 cm = 100 × 0.01 = 1 metre. From there: 1,000 mm; 0.001 km; 39.3701 inches; 3.2808 feet; 1.0936 yards; 0.0006 miles.
How It Works, In Plain Words
This converter routes every length through the metre, the international standard unit. Each unit carries an exact factor in metres: a millimetre is 0.001, a centimetre 0.01, a kilometre 1,000, an inch 0.0254, a foot 0.3048, a yard 0.9144 and a mile 1,609.344. Step one multiplies your value by its own unit’s factor, turning it into metres. Step two divides that metre figure by each of the other seven factors in turn, which is how a single click produces all eight rows. Follow the worked example: 100 cm × 0.01 gives exactly 1 metre; from there, dividing by 0.001 gives 1,000 mm, by 1,000 gives 0.001 km, by 0.0254 gives 39.3701 inches and by 0.3048 gives 3.2808 feet. Because every answer comes from the same metre value and the same exact factors, the rows always agree with each other — converting 100 cm to feet directly or via metres cannot give two different answers. Each result is rounded to at most four decimal places, with trailing zeros dropped and thousands separators added.
Real-World Uses
Comparing product sizes while shopping. The Benefits list makes this point: a listing in inches meets a tape measure marked in centimetres, and this page’s one result shows both — remember 1 inch = 2.54 cm exactly, so the comparison is precise, not estimated. Checking a height. A height given as 100 cm is 3.2808 ft — about 3 feet 3.37 inches, as the FAQ below explains — which is how metric heights translate into the feet-and-inches form many forms still ask for. Planning travel distances. A route described in miles converts to kilometres with the exact factor — 1 mile = 1.609344 km — and the same click shows metres and yards for shorter legs of the trip. Measuring for a DIY job. Timber, fabric and flooring are sold in mixed units; converting the room measurement once, into every unit, means the figure is ready whichever unit the merchant prices in.
Benefits
- All eight common length units in one result — no repeated conversions
- Exact international conversion factors, not rough estimates
- Both metric and imperial shown together for shopping, travel and engineering
- Handy for comparing product sizes listed in different units
Features of Our Tool
- Instant results in your browser
- No sign-up, no download, 100% free
- Works on mobile, tablet and desktop
- Clear step-by-step explanation below the tool
- Private — your entries never leave your device.
Common Mistakes
- Confusing inches with centimetres (1 inch = 2.54 cm, not 1 cm) — the costliest everyday conversion error
- Entering feet-and-inches as a decimal (5 ft 6 in is 5.5 ft, not 5.6 ft)
- Rounding too early in multi-step calculations — convert with full precision and round only at the end
Common Mistakes to Avoid
The mistakes list above covers the inch–centimetre confusion, the feet-and-inches decimal trap and early rounding, and a few more habits deserve care. The first is choosing the wrong From unit: 100 entered as millimetres instead of centimetres gives a length a tenth of the intended size, and the tool converts exactly what it is told. The second is treating the rounded display as exact in long chains: miles are shown to four decimal places, so 100 cm reads 0.0006 mi even though the unrounded figure is 0.000621 — fine for reading, but use the metre or centimetre row for further maths. The third is mixing area into a length job: this tool converts lengths only, so square units belong to the Square Footage Calculator linked below.
FAQ
How many centimetres are in an inch?
1 inch = 2.54 cm exactly.
How do I convert 100 cm to feet and inches?
100 cm = 3.2808 ft, which is about 3 feet 3.37 inches.
How many feet are in a metre?
1 metre = 3.2808 feet.
How many kilometres are in a mile?
1 mile = 1.609344 km exactly.
Why does 100 cm show as 0.0006 miles?
A mile is very long compared with a centimetre — 100 cm is just 0.000621 miles, shown rounded to 0.0006.
Can I convert a height given in feet and inches?
Yes, in two steps. The mistakes list gives the pattern: 5 ft 6 in is 5.5 ft, not 5.6 ft — convert the inches part into a fraction of a foot first, then enter the decimal feet value here and read off centimetres or metres.
Why do some results show fewer decimal places than others?
The tool rounds each result to at most four decimal places and drops trailing zeros. That is why the worked example shows a clean 1 m and 0.001 km, but 39.3701 in and 3.2808 ft where the extra places carry real information.