Common converters
Length Converter
Convert between metric, US customary and imperial length units.
Result
3.28084 ft
1 m = 3.28084 ft
All units for this value
| Unit | Symbol | Value |
|---|---|---|
| Nanometer | nm | 1000000000 |
| Micrometer | µm | 1000000 |
| Millimeter | mm | 1000 |
| Centimeter | cm | 100 |
| Decimeter | dm | 10 |
| Meter | m | 1 |
| Kilometer | km | 0.001 |
| Mil (thou) | mil | 39370.1 |
| Inch | in | 39.3701 |
| Foot | ft | 3.28084 |
| Yard | yd | 1.09361 |
| Fathom | fathom | 0.546807 |
| Furlong | fur | 0.00497097 |
| Mile | mi | 0.000621371 |
| Nautical mile | nmi | 0.000539957 |
| Astronomical unit | AU | 6.68459e-12 |
| Light-year | ly | 1.05700e-16 |
About this calculator
Length conversion turns a distance measured in one unit into the equivalent distance in another, whether you are moving between metric units like metres and kilometres or older units like feet, miles, and nautical miles. It is useful for travel planning, construction, sewing, science homework, and comparing measurements from different countries or eras.
How it works in plain English
Every length unit can be linked back to a single base unit, the metre, through a fixed multiplication factor. To convert, the tool multiplies the number you enter by the factor for your starting unit, which gives a value in metres, and then divides by the factor for the unit you want, or equivalently multiplies by a combined ratio calculated once for accuracy. This two-step chain avoids rounding errors that can creep in when converting directly between two unusual units.
Metric units such as millimetres, centimetres, metres, and kilometres scale by powers of ten, so their factors are simple. Imperial and US customary units such as inches, feet, yards, and miles use fixed historical ratios that were standardized in the twentieth century, while nautical miles are based on a minute of latitude and light-years are based on the distance light travels in a vacuum in one Julian year.
To use the tool, choose the unit you are converting from and the unit you want, then type a number. The result updates immediately as you type, and a table below shows the same value expressed in every supported length unit at once, so you can compare several units side by side without repeating the calculation. You can also adjust how many decimal places are shown for finer or coarser precision.
The formula
- value_in_metres = value x factor_from
- result = value_in_metres / factor_to
- 1 in = 0.0254 m, 1 ft = 0.3048 m, 1 mi = 1609.344 m, 1 nmi = 1852 m
Worked example
Suppose you want to know how many metres are in 5 miles. First the tool converts 5 miles into metres using the fixed factor for miles: 5 x 1609.344, which gives 8046.72 metres.
If you instead wanted feet, the tool would take that same 8046.72 metres and divide by the feet factor, 0.3048, giving 26,400 feet. Because both conversions pass through the same metre-based value, the two results stay perfectly consistent with each other, and you can trust that switching the target unit never changes the underlying distance being described, only how it is expressed.
Common length units and their metric equivalents
| Unit | Symbol | In metres |
|---|---|---|
| Millimetre | mm | 0.001 |
| Centimetre | cm | 0.01 |
| Metre | m | 1 |
| Kilometre | km | 1000 |
| Inch | in | 0.0254 |
| Foot | ft | 0.3048 |
| Mile | mi | 1609.344 |
| Nautical mile | nmi | 1852 |
| Light-year | ly | 9460730472580800 |
Factors are the internationally agreed definitions of these units.
Frequently asked questions
Why do inches and feet have such precise decimal factors?
In 1959, several English-speaking countries agreed to define the inch as exactly 0.0254 metres, which made the foot exactly 0.3048 metres and the mile exactly 1609.344 metres. Before that agreement, slightly different definitions existed in different countries, so this standardization made international conversions consistent and repeatable.
What is the difference between a mile and a nautical mile?
A standard mile, used on land, equals 1609.344 metres. A nautical mile equals 1852 metres and is based on one minute of latitude along the Earth's surface, which makes it especially useful for sea and air navigation where positions are described using latitude and longitude.
How is a light-year a unit of length rather than time?
A light-year measures the distance light travels through a vacuum in one year, not the year itself. Because the speed of light is constant, this distance is fixed and enormous, roughly 9.46 trillion kilometres, making it a convenient unit for describing distances between stars and galaxies.
Can I convert between metric and imperial units accurately?
Yes. The tool converts every unit through a common base unit, the metre, using exact defined factors, so conversions between metric units like kilometres and imperial units like miles are just as accurate as conversions within the same system, with no extra rounding introduced.
How do I see a value in several length units at once?
After entering a value and choosing a starting unit, the results table lists that same value converted into every other supported length unit simultaneously. This lets you compare, for example, a room's width in metres, feet, and inches all at the same time without re-entering the number.
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