On this page
Formula
Target value = Value × (Factor of source unit ÷ Factor of target unit)
- Value
- the length you type in
- Factor
- how many meters one of that unit equals (1 in = 0.0254 m, 1 ft = 0.3048 m, 1 mi = 1,609.344 m, 1 nmi = 1,852 m)
- Target value
- the same length expressed in the unit you convert to
What this length converter does
A length converter changes a measurement from one unit to another without changing the distance itself. This one covers the nine units people actually meet: millimeters, centimeters, meters and kilometers on the metric side; inches, feet, yards and miles in the US customary system; and the nautical mile used at sea and in aviation.
Type a number, choose the unit you have and the unit you want, and the answer appears straight away. Underneath, a table lists the same length in every other unit, so you can read off meters, feet and miles from one entry instead of running three conversions. The working line shows the exact multiplier used.
Length converter formula: how to convert by hand
Every unit in the converter is defined as a fixed number of meters. To convert, multiply by the source unit’s size in meters, then divide by the target unit’s size in meters. You never need a separate table for each pair.
Take a 2.4 m ceiling and convert it to feet:
- 2.4 m is already in meters.
- A foot is 0.3048 m, so 2.4 ÷ 0.3048 = 7.874 ft.
- To get feet and inches, take the 0.874 ft remainder and multiply by 12: 0.874 × 12 = 10.49 in. The ceiling is about 7 ft 10½ in.
The same two-step pattern works for anything. A 400 m running track lap is 400 ÷ 1,609.344 = 0.2485 miles, just under a quarter mile.
Length converter chart: exact factors
These are the exact definitions the converter uses, plus the relationships inside each system. The US customary units link to the metric system through the inch, which has been exactly 2.54 cm since 1959.
| Unit | Symbol | In meters (exact) | Within its own system |
|---|---|---|---|
| Millimeter | mm | 0.001 | 10 mm = 1 cm |
| Centimeter | cm | 0.01 | 100 cm = 1 m |
| Meter | m | 1 | 1,000 m = 1 km |
| Kilometer | km | 1,000 | — |
| Inch | in | 0.0254 | 12 in = 1 ft |
| Foot | ft | 0.3048 | 3 ft = 1 yd |
| Yard | yd | 0.9144 | 1,760 yd = 1 mi |
| Mile | mi | 1,609.344 | 5,280 ft = 1 mi |
| Nautical mile | nmi | 1,852 | about 6,076 ft |
Metric to imperial: the conversions people search most
| Conversion | Multiply by | Quick example |
|---|---|---|
| Feet to meters | 0.3048 | 8 ft = 2.4384 m |
| Meters to feet | 3.28084 | 100 m = 328.08 ft |
| Inches to millimeters | 25.4 | 0.5 in = 12.7 mm |
| Millimeters to inches | 0.0393701 | 19 mm = 0.748 in |
| Kilometers to miles | 0.621371 | 42.195 km = 26.22 mi |
| Miles to kilometers | 1.609344 | 3 mi = 4.828 km |
| Yards to meters | 0.9144 | 100 yd = 91.44 m |
| Nautical miles to kilometers | 1.852 | 20 nmi = 37.04 km |
Values were calculated with the converter’s own factors and rounded for display.
Where each unit is used
- Millimeters and inches dominate small measurements: screws, drill bits, rainfall, screen thickness. Woodworkers in the US read fractions of an inch, while hardware made overseas is labeled in millimeters.
- Centimeters are the everyday metric unit for bodies and objects, from heights to box sizes. For heights and clothing, the cm to inches converter adds feet-and-inches and tape-measure fractions.
- Feet and meters cover rooms, buildings and elevation. Floor plans in the US use feet; once you have the room’s dimensions, the square footage calculator turns them into area.
- Miles and kilometers are for roads and races. Road signs in the US are in miles, while race names such as 5K and 10K are metric.
- Nautical miles are the standard for charts, marine navigation and flight planning, because one nautical mile spans one minute of latitude. Speeds in nautical miles per hour are knots, which the speed converter handles.
Common mistakes with length units
- Reading decimal feet as feet and inches. 5.5 ft is 5 ft 6 in, not 5 ft 5 in. Multiply the decimal part by 12 to get inches.
- Mixing up miles and nautical miles. A 15-mile trip and a 15-nautical-mile passage differ by more than 2 miles.
- Rounding too early. Using 3.3 instead of 3.28084 feet per meter adds about 0.6% error, which on a 50 m pool is roughly a foot.
- Using the survey foot. Older US land records used a survey foot that differs from the international foot by 2 parts per million. It matters only for surveying over long distances, and it was retired at the end of 2022.
- Confusing length with area or volume. One meter is 3.28 ft, but a square meter is 10.76 sq ft and a cubic meter is 35.31 cu ft. Square and cube the factor, or use the volume converter for capacity.
Glossary
- Statute mile: the ordinary land mile of 5,280 feet, as opposed to the nautical mile.
- International foot: the foot of exactly 0.3048 m used in the US and worldwide since 1959.
- SI base unit: the meter is the base unit of length in the International System of Units. Every other unit here is defined from it.
Worked examples
Marathon distance in kilometers
A marathon is 26.2 miles. Convert it to kilometers.
Inputs: Value = 26.2; From = Miles (mi); To = Kilometers (km)
26.2 mi × 1.609344 = 42.164813 km
Answer: 26.2 mi = 42.164813 km
Room length in meters
A room is 12 feet long. How many meters is that?
Inputs: Value = 12; From = Feet (ft); To = Meters (m)
12 ft × 0.3048 = 3.6576 m
Answer: 12 ft = 3.6576 m
5K race in miles
A 5K race is 5,000 meters. Convert it to miles.
Inputs: Value = 5000; From = Meters (m); To = Miles (mi)
5,000 m × 0.0006213712 = 3.106856 mi
Answer: 5,000 m = 3.106856 mi
Nautical mile vs statute mile (edge case)
One nautical mile (exactly 1,852 m) expressed in ordinary statute miles.
Inputs: Value = 1; From = Nautical miles (nmi); To = Miles (mi)
1 nmi × 1.150779448 = 1.150779 mi
Answer: 1 nmi = 1.150779 mi
Assumptions and limitations
- Every factor is an exact definition. The inch is exactly 2.54 cm (international yard and pound agreement of 1959), and the nautical mile is exactly 1,852 m.
- Feet, yards and miles are the international units. The old US survey foot (1200/3937 m), retired at the end of 2022, is not used.
- Results are shown to up to 6 decimal places, so a few digits are rounded in long conversions such as nautical miles to inches.
- Lengths can't be negative. For a person's height in feet and inches, use the cm to inches converter, which also splits the result into feet plus inches.
Frequently asked questions
How many feet are in a meter?
One meter is 3.28084 feet, because a foot is defined as exactly 0.3048 m and 1 ÷ 0.3048 = 3.280839895. For rough work, a meter is a little over 3 feet 3 inches.
How do you convert kilometers to miles?
Divide by 1.609344, or multiply by 0.621371. A 10 km race is 10 × 0.621371 = 6.21 miles. Going the other way, multiply miles by 1.609344.
Is a nautical mile the same as a mile?
No. A nautical mile is exactly 1,852 meters, about 1.15 ordinary (statute) miles. It comes from one minute of latitude, which is why ships and aircraft use it together with knots.
What is the easiest way to convert metric to imperial length?
Remember three anchors. An inch is 2.54 cm, a foot is 30.48 cm, and a mile is about 1.61 km. Every other conversion follows from those by multiplying or dividing by 12, 3 or 1,760.
How many millimeters are in an inch?
Exactly 25.4 mm. So 6 mm is 6 ÷ 25.4 = 0.236 in, a little under a quarter inch, and a 3/8-inch bolt is 9.525 mm across.
Why does my converted value have so many decimals?
Metric and US units are not round multiples of each other, so most conversions produce long decimals. The converter keeps 6 decimal places for accuracy. Round the result to the precision your tape measure or map can actually show.
Sources
- SI Units – Length — National Institute of Standards and Technology (NIST). Checked October 12, 2026.
- NIST Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically — National Institute of Standards and Technology (NIST). Checked October 12, 2026.
- U.S. Survey Foot — National Institute of Standards and Technology (NIST). Checked October 12, 2026.