Length Converter
Convert between millimeters, centimeters, meters, kilometers, inches, feet, yards, and miles.
How it works
This converter handles length and distance across both the metric system (millimeters through kilometers) and the imperial/US customary system (inches through miles), plus nautical miles for maritime and aviation use.
The conversion works through a base unit: your input value is first converted to meters, then from meters into whatever unit you've selected as the target. This two-step approach (rather than a separate formula for every possible pair of units) is why the calculator can convert cleanly between any two of its supported units, metric or imperial, in either direction.
Some conversions come up constantly in everyday life: converting kilometers to miles for running distances or road trip planning, centimeters to inches for height or furniture dimensions, and meters to feet for construction or real estate measurements. A quick mental approximation — multiply kilometers by 0.62 to estimate miles, or divide centimeters by 2.5 to estimate inches — gets you close, but this calculator uses the exact defined conversion factors for precise results.
Those exact factors are internationally defined constants, not rounded approximations: 1 inch is exactly 2.54 centimeters, and 1 mile is exactly 1,609.344 meters, by international agreement since 1959. Every other imperial length unit (feet, yards) derives from the inch, so conversions carry through with no accumulated rounding error.
The metric system, used by nearly every country, is based on powers of 10 (1 km = 1,000 m = 100,000 cm), which makes unit conversion within it purely a matter of shifting a decimal point. The US, along with a small number of other countries, still primarily uses the imperial/US customary system for everyday measurements, which is why converters like this one get so much use for travel, trade, and international communication.
Metrication — the process of countries switching to the metric system — has been underway since France first adopted it in the 1790s. Most of the world completed the transition over the 19th and 20th centuries; the UK officially metricated for most purposes but kept miles for road distances, while the US never mandated the switch for everyday use despite formally recognizing the metric system since 1866.
Length units also show up heavily in specialized contexts: sports track events are measured in meters internationally (the 100m, 400m, marathon in km) even in countries that use imperial units elsewhere, aviation measures altitude in feet worldwide by international convention, and construction drawings often mix units depending on the country and trade — all situations where a quick, precise converter like this one is genuinely useful rather than just academic.
How many meters are in a mile?
1 mile = 1609.344 meters.
What's the difference between metric and imperial units?
Metric units (meters, kilometers, centimeters) scale by powers of 10 and are used by most of the world. Imperial/US customary units (inches, feet, miles) use less regular scaling factors and are primarily used in the United States and a few other countries.
How do I convert my height from centimeters to feet and inches?
Convert centimeters to inches first (divide by 2.54), then divide by 12 to get feet, with the remainder as leftover inches — for example, 175 cm ≈ 68.9 inches ≈ 5 feet 9 inches.
Why do the US and UK use different measurement systems?
The UK has officially adopted the metric system for most purposes (though some imperial units persist in everyday use, like miles for road distances), while the US never fully converted from the imperial system it inherited from British colonial measurement standards.
What's a nautical mile, and how is it different from a regular mile?
A nautical mile (1,852 meters) is based on the Earth's circumference — one minute of latitude — and is used in maritime and aviation navigation, making it about 15% longer than a standard (statute) mile of 1,609.344 meters.
How precise are these conversions?
Fully precise — the calculator uses internationally defined exact conversion factors (not rounded approximations), so results are limited only by the display precision shown, not by the underlying math.
Can I convert between more than two units at once?
Yes — below the main From/To conversion, the "Quick reference" table shows your entered value converted into every other supported unit simultaneously.
When did the metric system become standard?
France adopted it first in the 1790s, and most countries converted over the 19th and 20th centuries. The US formally recognized the metric system in 1866 but never mandated it for everyday use, unlike most of the rest of the world.
Why do aviation and sports use specific units regardless of country?
Aviation measures altitude in feet worldwide by international convention for safety consistency across airspaces, while international sports events (track and field, swimming) use meters even in countries that use imperial units for everyday measurement.