Length Converter
Convert between metric and US units of length — mm, cm, m, km, inches, feet, yards, miles and nautical miles — with the exact formula for every pair.
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- 27 categoriesFrom length to data storage
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How to use this tool
Steps for using the Unit Converter.
- Type a number into From — kilometers are preselected. Commas and scientific notation such as 2.5e3 are accepted.
- Pick the units to convert between; the result in miles (or whichever unit you choose) updates as you type. Use the swap button to reverse the conversion.
- Set the decimal places, turn on Show formula to see the calculation, and copy or share the result.
- Below the converter, the table lists every length unit with its exact definition, and the links open dedicated pages for the most common pairs.
Example
5.5 kilometers to miles
5.5 km3.417542 mi
Formula: mi = km ÷ 1.609344Common use cases
- Converting heights, room dimensions and furniture sizes between metric and imperial.
- Running, cycling and driving distances in km and miles.
- Engineering drawings and 3D printing that mix millimeters and inches.
Length unit table
| Unit | Symbol | System | Definition | In meters |
|---|---|---|---|---|
| Millimeter | mm | Metric | 1/1000 m | 0.001 |
| Centimeter | cm | Metric | 1/100 m | 0.01 |
| Meter | m | SI | SI base unit of length | 1 |
| Kilometer | km | Metric | 1,000 m | 1,000 |
| Inch | in | US customary | Exactly 2.54 cm | 0.0254 |
| Foot | ft | US customary | 12 in = exactly 0.3048 m | 0.3048 |
| Yard | yd | US customary | 3 ft = exactly 0.9144 m | 0.9144 |
| Mile | mi | US customary | 5,280 ft = exactly 1,609.344 m | 1,609.344 |
| Nautical mile | nmi | Other | Exactly 1,852 m | 1,852 |
Popular length conversions
- Meters to feet converter1 m = 3.28084 ft
- Feet to meters converter1 ft = 0.3048 m
- Kilometers to miles converter1 km = 0.621371 mi
- Miles to kilometers converter1 mi = 1.609344 km
- Centimeters to inches converter1 cm = 0.393701 in
- Inches to centimeters converter1 in = 2.54 cm
- Millimeters to inches converter1 mm = 0.03937 in
- Yards to meters converter1 yd = 0.9144 m
Other unit converters
- Weight convertermg · g · kg · t · oz · lb · st
- Speed converterm/s · km/h · mph · ft/s · kn
- Volume convertermL · L · cm³ · m³ · gal (US) · qt (US) · cup (US) · fl oz (US) · gal (UK) · fl oz (UK)
- Temperature converter°C · °F · K
- Area convertermm² · cm² · m² · km² · in² · ft² · yd² · ac · ha
- Time converterms · s · min · h · d · wk
- Angle converter° · rad · gon · ′ · ″ · tr
- Pressure converterPa · kPa · MPa · bar · mbar · psi · atm · Torr · mmHg
About length units
The meter is the SI base unit of length. Metric units differ by powers of ten (1 km = 1,000 m, 1 m = 100 cm = 1,000 mm), so converting between them only moves the decimal point.
US customary units are defined from the meter: since 1959 the international inch is exactly 2.54 cm, so the foot is exactly 0.3048 m, the yard 0.9144 m and the mile 1,609.344 m. The nautical mile (exactly 1,852 m) is used at sea and in aviation because it corresponds to about one arcminute of latitude.
Limitations
- Results are rounded for display only; the calculation keeps full precision (15 significant digits).
Frequently asked questions
How many feet are in a meter?
1 meter = 3.28084 feet (exactly 1 ÷ 0.3048). One foot is exactly 0.3048 m.
Is a mile the same as a nautical mile?
No. A statute mile is 1,609.344 m; a nautical mile is 1,852 m — about 15% longer.
Why are inches defined in centimeters?
Since the 1959 international yard and pound agreement, the inch has been defined as exactly 2.54 cm, so every US length unit has an exact metric equivalent.
Are these length conversions exact?
Each unit is defined from its official definition (for example 1 inch = 2.54 cm exactly). Results are calculated in double precision and only rounded to the decimal places you choose when shown.