Length Converter
Convert between metric and imperial length units.
Results update as you type.
How it works
A length converter turns a distance expressed in one unit into its equivalent in another, spanning metric units like millimetres, centimetres, metres and kilometres and imperial units like inches, feet, yards and miles. It works by reducing your value to metres, the base unit, and then scaling out to whatever unit you select, so a single mechanism covers every pairing across both systems. This matters because metric and imperial live side by side in everyday life, and mixing them causes real errors. Furniture measured in centimetres has to fit a room quoted in feet; an overseas recipe, a running route or a construction spec may arrive in the system you do not use daily. A length converter removes the guesswork and the risk of a slipped decimal that turns a sensible number into a nonsense one. The normalise-to-metres approach is used because every length unit has a fixed, internationally defined ratio to the metre — one inch is exactly 0.0254 m, one mile is 1,609.344 m — so pivoting through that base keeps results exact rather than approximate. Students, tradespeople, travellers, engineers and online shoppers all reach for a length converter whenever a measurement shows up in the wrong unit.
Convert to metres via known factors, then to the target unit
The input is multiplied by its unit's fixed ratio to the metre to get a value in metres, then divided by the target unit's ratio to reach the answer. This two-step pivot works because every length unit is defined as a constant number of metres, so chaining through the shared base is algebraically exact and avoids storing a separate factor for each of the many unit pairs.
Source:International System of Units (SI) — NIST
We review all our tools from time to time to ensure accuracy.
Worked example
How to use this calculator
- 1
Enter your values
Enter value, from and to.
- 2
Adjust the options
Fine-tune any options to match your situation.
- 3
Read your result
Converted length updates instantly as you type — no button to press.
Frequently asked questions
How many centimetres are in an inch?
Exactly 2.54 centimetres, by international definition since 1959. This is not a rounded figure but an exact one, which is why inch-to-centimetre conversions are precise. It follows that one foot is 30.48 cm and one metre is about 39.37 inches. Because the definition is exact, any rounding you see comes only from the number of decimal places displayed, not the underlying factor.
How do I convert miles to kilometres?
Multiply the number of miles by 1.609344 to get kilometres. So 5 miles is about 8.05 km, and a 26.2-mile marathon is roughly 42.2 km. To go the other way, divide kilometres by 1.609344, or multiply by about 0.6214. The factor is exact because a mile is defined as exactly 1,609.344 metres, or 1,760 yards.
How many feet are in a metre?
One metre is about 3.2808 feet, since a foot is defined as exactly 0.3048 metres. That means 10 metres is roughly 32.81 feet. For a quick mental estimate, a metre is a little over three feet three inches. The exact route is to divide the metre value by 0.3048, which the converter does automatically to the displayed precision.
Are the conversions exact?
Yes. The converter uses the internationally defined factors, all of which tie back to the metre, so results are accurate to the decimals shown. Where you see a rounded figure such as 39.3701 inches, the rounding is purely for display; the calculation itself carries full precision. Metric-to-imperial factors like the inch and mile are exact definitions rather than measured approximations.
What is the difference between metric and imperial length units?
Metric units — millimetre, centimetre, metre, kilometre — scale in powers of ten, making conversions within the system simple shifts of the decimal point. Imperial units — inch, foot, yard, mile — use varied factors of 12, 3 and 1,760. Most of the world uses metric, while the US and, informally, the UK retain imperial for some purposes, which is exactly why a converter between the two is so useful.