To convert length between metric and imperial units, multiply by a fixed factor: 1 inch is exactly 2.54 centimeters, 1 foot is exactly 0.3048 meters, and 1 mile is exactly 1.609344 kilometers. A length converter applies those factors for you: type a number, pick two units, and read the answer.
These factors are exact by definition. Since an international agreement in 1959, the inch, foot, yard and mile have been defined in terms of the meter, so every metric-to-imperial length conversion has one correct answer. This guide gives you the factors, shows how to use them by hand, and points out where people usually go wrong.
Length conversion factors for common units
Every length unit can be expressed in meters. Once you know a unit's size in meters, converting between any two units takes one multiplication and one division.
| Unit | Size in meters | Handy equivalent |
|---|---|---|
| Millimeter (mm) | 0.001 | 0.0394 in |
| Centimeter (cm) | 0.01 | 0.3937 in |
| Inch (in) | 0.0254 | 2.54 cm |
| Foot (ft) | 0.3048 | 12 in |
| Yard (yd) | 0.9144 | 3 ft |
| Meter (m) | 1 | 3.2808 ft |
| Kilometer (km) | 1,000 | 0.6214 mi |
| Mile (mi) | 1,609.344 | 5,280 ft |
The length conversion formula
result = value × (meters per "from" unit) ÷ (meters per "to" unit)This is the same method the converter uses: it turns your value into meters, then turns meters into the unit you asked for. Because every unit passes through the meter, you can go directly from inches to kilometers or from millimeters to yards without a separate table for each pair.
How to convert meters to feet, cm to inches and km to miles
Meters to feet
Convert 2.5 meters to feet:
- 2.5 × 1 = 2.5 meters.
- 2.5 ÷ 0.3048 = 8.2021 feet.
- For feet and inches, multiply the decimal part by 12: 0.2021 × 12 = 2.4 inches. So 2.5 m is about 8 ft 2.4 in.
Height in feet and inches to centimeters
Convert 5 ft 10 in to centimeters:
- Turn the whole height into inches: 5 × 12 + 10 = 70 inches.
- Multiply by 2.54: 70 × 2.54 = 177.8 cm.
Going the other way, divide centimeters by 2.54 to get inches, then divide by 12. For example, 180 cm ÷ 2.54 = 70.87 inches, which is 5 ft 10.87 in.
Health tools often need body measurements in one specific unit. The BMI calculator takes height in centimeters or inches, and the body fat calculator asks for height, neck and waist in centimeters, so convert tape-measure readings in inches first. Our guide to BMI basics explains how height is used.
Kilometers to miles for running and driving
Divide kilometers by 1.609344. A 10 km race is 10 ÷ 1.609344 = 6.2137 miles, a half marathon (21.0975 km) is 13.1094 miles, and a marathon (42.195 km) is 26.2188 miles. Speed units are built from distance units, so the same factor drives the speed converter when you turn km/h into mph; see our guide to speed conversions for details.
Quick mental approximations
When you only need a rough figure, these shortcuts are close enough:
- Kilometers to miles: multiply by 0.6. Eight kilometers is about 5 miles (exactly 4.97).
- Meters to feet: multiply by 3.3. Ten meters is about 33 feet (exactly 32.81).
- Inches to centimeters: multiply by 2.5. This runs about 1.6% low, so use 2.54 for anything you plan to cut or build.
How to use the Length Converter
- Open the Length Converter.
- Type your number in the Value field. Decimals such as 5.75 work; negative numbers are rejected because a length cannot be below zero.
- Choose the unit you have from the From list: meters, kilometers, centimeters, millimeters, miles, yards, feet or inches.
- Choose the unit you want from the To list.
- Read the Result, rounded to four decimal places. It updates as you type, so there is no button to press.
- Click the swap button between the two lists to reverse the direction, for example to turn a feet-to-meters conversion into meters-to-feet.
The tool takes one value in one unit. To convert a mixed measurement like 5 ft 10 in, enter it as a single number first: 70 inches, or 5.8333 feet.
Common length conversion mistakes
- Treating a meter as 3 feet. A meter is 3.28 feet, and the gap grows with distance: 100 m is 328 ft, not 300.
- Reading feet and inches as a decimal. 5 ft 6 in is 5.5 ft, not 5.6 ft. Divide the inches by 12 before you convert.
- Rounding the factor too early. Using 1.6 for a mile works for a quick estimate, but over 500 miles it gives 800 km instead of 804.67 km. Keep full precision until the final step.
- Converting area with a length factor. Square units scale by the square of the factor, so 1 square meter is 10.7639 square feet, not 3.28. Use the area converter for floor plans and land, and read our area conversion guide to see why.
- Mixing up survey feet. Some older US land records use the US survey foot, which is about 2 parts per million longer than the international foot. It only matters over long survey distances, but it explains small mismatches in property data.
Most countries use metric units for everyday length. The United States uses feet, inches and miles for most daily purposes, and the United Kingdom still uses miles on road signs and often quotes height in feet and inches. If you work across both systems, keep the exact factors handy or let the converter do the arithmetic.
Frequently asked questions
How many feet are in a meter?
One meter equals 3.28084 feet, or about 3 feet 3.37 inches. To convert meters to feet, divide the number of meters by 0.3048.
How do I convert centimeters to inches?
Divide centimeters by 2.54. For example, 30 cm ÷ 2.54 = 11.811 inches. To go from inches to centimeters, multiply by 2.54.
How many kilometers are in a mile?
One mile is exactly 1.609344 kilometers, and one kilometer is about 0.621371 miles. A quick estimate is to multiply kilometers by 0.6.
How do I convert my height from cm to feet and inches?
Divide your height in centimeters by 2.54 to get inches, then divide by 12. The whole number is feet and the remainder is inches, so 180 cm is 70.87 inches, or 5 ft 10.87 in.
Is a yard longer than a meter?
No. A yard is 0.9144 meters, so a meter is about 9% longer at 1.0936 yards.
Why is an inch exactly 2.54 centimeters?
Since 1959, the international inch has been defined as exactly 25.4 millimeters. That definition fixes the foot at 0.3048 m and the mile at 1,609.344 m, so these conversions are exact rather than measured.