Convert Between Length & Distance Units Convert between millimeters, centimeters, meters, kilometers, inches, feet, yards, miles, and nautical miles instantly.

All length conversions in this tool are based on the international yard and pound agreement of 1959, which defined the inch as exactly 25.4 millimeters. From this single definition, every imperial-to-metric length conversion can be derived exactly:

• 1 foot = 12 inches = 304.8 mm
• 1 yard = 3 feet = 914.4 mm
• 1 mile = 5,280 feet = 1,609.344 m

The meter itself is now defined by the speed of light: it is the distance light travels in vacuum in 1/299,792,458 of a second, making it the most precisely defined unit of length.

The nautical mile is defined by international agreement as exactly 1,852 meters. It originated from the practice of measuring one minute of arc of latitude, but the modern definition is independent of Earth's geometry.

Our converter multiplies the input value by the source unit's factor (converting to meters) and divides by the target unit's factor. This two-step approach through a common base unit ensures accuracy and makes it easy to add new units. Floating-point precision is managed by displaying up to 10 significant digits, which exceeds the precision of any physical measurement you're likely to encounter.