How to use the Length Converter
- Type the length you want to convert. Decimals, fractions such as 3/4 and heights written like 5′10″ or 5 ft 10 in all work.
- Choose the unit to convert from and the unit to convert to, or press the swap button to reverse them.
- Read the answer in the result box, together with the one-unit factor in both directions and a feet-and-inches version when it helps.
- Scroll the full list to see the same length in every unit, and click any figure to copy it.
Features
- Exact international definitions: 1 inch = 2.54 cm, 1 mile = 1,609.344 m
- Heights in feet and inches, in and out
- 19 units from nanometers to parsecs
- Your value in every unit at once, click to copy
- Automatic precision or a fixed number of decimal places
- Remembers your last conversion on this device
Where today’s length units come from
The meter was born in revolutionary France in the 1790s as one ten-millionth of the distance from the North Pole to the equator, measured along the meridian through Paris. Physical bars later stood in for that survey, and since 1983 the meter has been defined by nature itself: the distance light travels in a vacuum in 1/299,792,458 of a second. Every other metric length is a power of ten of the meter, which is why converting millimeters to kilometers only moves a decimal point.
The inch, foot, yard and mile are much older and once varied from town to town. In 1959 the United States, the United Kingdom, Canada, Australia, New Zealand and South Africa signed the International Yard and Pound Agreement, which fixed the yard at exactly 0.9144 meters. That single decision made the inch exactly 25.4 mm and the mile exactly 1,609.344 m, so every conversion on this page is exact, not an approximation. The older US survey foot, a hair longer at 1200/3937 m, was retired for new work at the end of 2022.
Which unit is used where
- Everyday metric (mm, cm, m, km) is used by almost every country and by science everywhere.
- Inches, feet and miles remain the daily units in the United States. The UK still uses miles on road signs and feet and inches for people’s height.
- Feet are the worldwide standard for aircraft altitude, while nautical miles (exactly 1,852 m, fixed by international agreement in 1929) measure distance at sea and in the air.
- Hands (4 inches) measure horse height, furlongs (one eighth of a mile) survive in horse racing, and fathoms (6 feet) describe water depth.
- Astronomical units, light-years and parsecs measure the solar system and the space between stars.
Worked examples
Height: 5 feet 10 inches in centimeters
First turn everything into inches: 5 × 12 + 10 = 70 inches. Then multiply by 2.54: 70 × 2.54 = 177.8 cm. You can type 5'10" straight into the converter to get the same answer.
Running: a 10K race in miles
Divide kilometers by 1.609344: 10 ÷ 1.609344 = 6.214 miles. A half marathon (21.0975 km) is about 13.11 miles.
DIY: a 2.4 m board in feet
Divide meters by 0.3048: 2.4 ÷ 0.3048 = 7.874 ft, which is 7 ft 10.5 in.
Quick reference
| Unit | In meters (exact) | Handy equivalent |
|---|---|---|
| 1 inch | 0.0254 | 2.54 cm |
| 1 foot | 0.3048 | 12 inches |
| 1 yard | 0.9144 | 3 feet |
| 1 mile | 1,609.344 | 5,280 feet |
| 1 nautical mile | 1,852 | about 1.151 miles |
| 1 fathom | 1.8288 | 6 feet |
Mistakes to avoid
Do not round 3.28084 feet per meter down to 3.28 for long distances: over a kilometer the error is more than 8 cm. Never mix up statute and nautical miles, which differ by about 15%. And when you need area or volume, convert the length first and then square or cube it, or use the Area Converter and Volume Converter, because 1 m is 3.28 ft but 1 m² is 10.76 ft².
Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54. The inch has been defined as 25.4 millimeters since the 1959 international agreement, so the factor never needs rounding.
How do I convert my height from feet and inches to centimeters?
Multiply the feet by 12, add the inches, then multiply the total by 2.54. Or type your height as 5′10″ or 5 ft 10 in into the converter and it does the steps for you.
How many feet are in a meter?
One meter is about 3.2808399 feet, which is 1 divided by 0.3048. For rough mental math, a meter is a little over 3 feet 3 inches.
What is the difference between a mile and a nautical mile?
A statute mile is 1,609.344 meters and is used on land. A nautical mile is 1,852 meters, about 1.151 statute miles, and is used at sea and in aviation because it is close to one minute of latitude.
Why do other converters give slightly different answers?
Most differences come from rounded factors, such as using 3.28 feet per meter, or from the old US survey foot. This tool uses the exact international definitions and shows up to 10 significant digits.