Calculator
Length Converter
Convert between metric and imperial length units.
How do metric and imperial length units relate?
Metric length units scale by powers of 10 (10mm = 1cm, 100cm = 1m, 1000m = 1km), which makes converting within the metric system just a matter of moving a decimal point. Imperial units don’t share that clean structure (12 inches = 1 foot, 3 feet = 1 yard, 5,280 feet = 1 mile), so converting between the two systems needs a proper conversion factor rather than a shortcut.
Frequently asked questions
What is the exact inch-to-centimeter conversion?
1 inch = 2.54 centimeters exactly, by international agreement since 1959. Every other inch-based conversion (feet to meters, miles to kilometers) derives from this one exact definition, which is why some converted values come out to long, non-round decimals.
Why do some conversions produce long decimal results?
Metric and imperial units weren't designed around a common base, so most cross-system conversions (like miles to kilometers, at 1.60934) aren't round numbers. The calculator shows results to 6 decimal places for precision, though real-world use rarely needs more than 2-3.
Which countries use imperial vs. metric for everyday length?
The metric system is the global standard for measurement in science, most countries' everyday use, and international trade. The United States remains the largest holdout using imperial units (inches, feet, miles) for everyday measurement, alongside limited use in the UK and a few other countries for specific applications like road distances.
Is a nautical mile the same as a regular mile?
No — a nautical mile (used in aviation and maritime navigation) is about 1.852 km, while a standard (statute) mile is about 1.609 km. They're defined differently: a nautical mile corresponds to one minute of latitude on the Earth's surface, while a statute mile has a historical land-measurement origin.