What this calculator does
Change a length from one unit to another, such as feet to meters or miles to kilometers. Metric and US lengths are tied together by one exact rule. Since 1959, one inch has been exactly 2.54 centimeters. Every other switch between the two systems follows from that one number.
Enter a length and pick the units to convert from and to. You'll see the answer, plus a table of the same length in every unit the converter knows.
Where it's used
Why this math matters outside the classroom:
- Trim and molding. A 2.4 m length of trim is about 94.5 in, or 7 ft 10½ in.
- Running. A 1,500 m race is about 0.93 miles, just short of a mile.
- Sailing. A course of 10 nautical miles is 18.52 km, or about 11.5 statute miles.
- Engineering drawings. Mechanics matching hardware find that a 0.25 in bolt diameter is exactly 6.35 mm.
- Metric prefixes. Students convert 3.5 km to 3,500 m and then to 350,000 cm by moving between metric prefixes.
Grade level and standards: Grades 5–6; Common Core State Standards for Mathematics 5.MD.A.1, 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter the length you want to convert. Zero and decimals are fine, but negative lengths aren't allowed.
- Choose the unit you're converting from and the unit you want.
- Read the converted value, or scan the table to see the length in all nine units at once. The working shows how many meters each unit is.
What the inputs mean
- Length
- The length to convert, in the “From” unit.
- From
- The unit your number is in.
- To
- The unit you want the answer in.
Formula and method
result = value × (size of the from-unit in meters) ÷ (size of the to-unit in meters) 1 in = 2.54 cm = 0.0254 m (exact) 1 ft = 12 in = 0.3048 m; 1 yd = 3 ft = 0.9144 m 1 mi = 5,280 ft = 1,609.344 m 1 nmi = 1,852 m (exact)
In the formulas, in is inches, ft is feet, yd is yards, mi is miles and nmi is nautical miles. On the metric side, m is meters and cm is centimeters.
The converter knows each unit's exact size in meters. To convert, it multiplies your number by the size of the unit you start with, which gives meters. Then it divides by the size of the unit you want. Every factor is an exact definition, so the only rounding is in how many decimals you choose to show.
The inch, foot, yard and mile are the international units fixed in 1959 by an agreement between English-speaking countries. The nautical mile is defined on its own as exactly 1,852 meters. It's used for finding your way at sea and in the air.
Worked example
Convert 5 feet to meters.
- 1 foot is exactly 0.3048 meters.
- Multiply your 5 feet by that size: 5 × 0.3048 = 1.524.
Result: 5 feet is exactly 1.524 meters, or 152.4 centimeters.
Understanding the result
Results are exact to the precision shown. For a quick check in your head, a meter is a little over 3 feet 3 inches. A kilometer is about 0.62 miles.
When you convert a measurement, keep only as many digits as the original measurement deserves. A board measured to the nearest inch doesn't become precise to the micrometer just because you converted it.
Assumptions and limitations
- US units follow the international definitions from 1959.
- The mile is the everyday statute mile of 5,280 feet. The nautical mile is the international nautical mile.
- It doesn't offer the older US survey foot (1200/3937 m). That foot differs from the international foot by about 2 parts per million.
- Units for space distances and for atom-sized lengths aren't included.
- It converts one value at a time. It doesn't combine mixed units, such as 5 ft 9 in, into one figure.
Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54. That's the definition of the inch, not a rounded figure, so 10 inches is exactly 25.4 cm.
What is the difference between a mile and a nautical mile?
A statute mile, the everyday mile, is 5,280 feet, or 1,609.344 meters. A nautical mile is 1,852 meters, about 15% longer. Nautical miles are used at sea and in aviation. A knot is one nautical mile per hour.
How do I convert 5 ft 9 in to centimeters?
Turn it into inches first: 5 × 12 + 9 = 69 inches. Then convert: 69 × 2.54 = 175.26 cm. You can also convert each part here and add the results.
Why does the converted value show so many decimal places?
Many conversions don't come out to round numbers. For example, 1 meter is 3.280839… feet. Use the precision control to show fewer decimals. The value underneath stays the same.
Is there a page for a single pair, such as cm to inches?
Yes. The most common length conversions have their own pages, each with a quick table and tips for that pair. They cover centimeters to inches, feet to meters, kilometers to miles, millimeters to inches and inches to feet. There are also pages for centimeters to feet, yards to meters, miles to feet, meters to inches and millimeters to centimeters. This converter handles every other combination.
How this calculator is checked
Method: International yard and pound agreement (1959): 1 in = 0.0254 m exactly; international nautical mile = 1,852 m exactly; SI prefixes for metric units. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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