Unit Converters guide
8 Everyday Length Conversions: Miles, Feet and Inches
· 3 min read
The key length conversions are exact: 1 inch = 2.54 cm, 1 foot = 30.48 cm, and 1 mile = 1.609344 km. Going the other way, 1 km is about 0.6214 miles and 1 meter is about 3.281 feet. Since 1959, imperial units have been officially defined in metric terms, so these factors aren't approximations; any rounding you see comes from the decimals you choose to keep.
Below are eight situations where people regularly need a length conversion, with the numbers worked out.
Exact factors worth remembering
| From | To | Multiply by |
|---|---|---|
| inches | centimeters | 2.54 (exact) |
| feet | meters | 0.3048 (exact) |
| yards | meters | 0.9144 (exact) |
| miles | kilometers | 1.609344 (exact) |
| nautical miles | meters | 1,852 (exact) |
| kilometers | miles | ≈ 0.6214 |
1. Running race distances
Race distances are set in kilometers almost everywhere, while many runners track their pace in miles.
- 5K = 3.11 miles (3.106855961)
- 10K = 6.21 miles
- Marathon, 42.195 km = 26.22 miles (26.21875746)
That last figure is why the marathon is usually quoted as "26.2 miles".
2. Height in feet and inches
Height is the conversion people most often get wrong, because 5 ft 9 in is not 5.9 feet. There are 12 inches in a foot, so 9 inches is 0.75 of a foot: 5 ft 9 in = 5.75 ft.
Simplest method: convert everything to inches first. 5 × 12 + 9 = 69 inches, and 69 × 2.54 = 175.26 cm. A height of 6 ft exactly is 1.8288 m.
3. TV and monitor sizes
Screens are sold by their diagonal in inches, even in metric countries. A 65-inch TV has a diagonal of 65 × 2.54 = 165.1 cm. That is the diagonal, not the width, so check the width separately before you buy a stand.
4. Bicycle wheels and tire sizes
A wheel listed as 27 inches is about 68.58 cm across. Wheel sizes are traditional names rather than precise measurements, so for tires, rely on the metric ISO size printed on the sidewall.
5. Sports fields
An American football field is 100 yards between the goal lines, which is 91.44 m. Most track events are measured in meters, so a 100 m sprint is a little longer than 100 yards.
6. Boating and flying
Ships and aircraft measure distance in nautical miles: 1 nmi = 1,852 m exactly, or about 1.1508 statute miles. A nautical mile was originally based on one minute of latitude, which is why it doesn't line up neatly with the land mile.
7. Small measurements
In engineering and DIY, millimeters and fractions of an inch meet. Half a millimeter is about 0.0197 inches, and a quarter inch is exactly 6.35 mm. For very small scales, the converter also covers micrometers (µm) and nanometers (nm), useful for things like filter ratings or wavelengths of light.
8. Road distances and signs
Driving in a country that uses the other system? 1 km is 0.6214 miles, so a sign reading 80 km is about 50 miles away. For speed limits, which are a different quantity, use the Speed Converter instead.
How to use the Length Converter
The Length Converter covers nanometers through to nautical miles:
- Enter a number in the Value field.
- Choose the units in From and To. The ⇄ button swaps them.
- Read the result, or scan the table underneath, which shows your value in every length unit at once: millimeters, centimeters, meters, kilometers, inches, feet, yards, miles and more.
Results show up to 10 significant digits, and extremely large or small values switch to scientific notation. The copy button copies the number without thousands separators, so it pastes cleanly into a spreadsheet. There is a single value field, so for feet-and-inches heights, convert to total inches or decimal feet first, as shown above.
Common mistakes
- Treating 5'9" as 5.9 feet. It is 5.75 feet.
- Confusing nautical and statute miles. They differ by about 15%.
- Converting area with length factors. A square foot is not 30.48 cm²; it is 30.48 × 30.48 = 929.0304 cm². For floor plans and land, use the Area Converter.
FAQ
Why is a mile 1.609344 km and not a rounder number?
The mile is defined as 5,280 feet, and the foot as exactly 0.3048 m. Multiply them and you get 1,609.344 m.
How many feet is a meter?
About 3.2808 feet, or 3 feet and roughly 3.37 inches. One meter is 39.37 inches.
Are US and UK inches the same?
Yes. Since the 1959 international agreement, the inch, foot, yard and mile have had the same length in both countries.
Convert any length, from nanometers to nautical miles, with the Length Converter.