Length Unit Converter
Full Reference Table
Enter a value above and click Convert to populate the table.
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About Length Units
Length measurement is fundamental to construction, navigation, science, and everyday life. Our free online length converter supports ten of the most commonly used units, from millimeters to light-years, and displays a full reference table for every conversion at once.
Metric vs Imperial Length Units
The world uses two major systems for measuring length. The metric system — used by most countries — is based on the meter as the fundamental unit. Multiples and fractions are always powers of ten, making calculations straightforward: 1 kilometer = 1,000 meters; 1 centimeter = 0.01 meters; 1 millimeter = 0.001 meters.
The imperial system, still in common use in the United States and the United Kingdom for everyday measurements, uses feet, inches, yards, and miles. These units have less intuitive relationships: 1 foot = 12 inches; 1 yard = 3 feet; 1 mile = 5,280 feet = 1,760 yards.
Key Conversion Facts
- 1 meter = 3.28084 feet
- 1 kilometer = 0.621371 miles
- 1 inch = 2.54 centimeters
- 1 mile = 1,609.344 meters
- 1 nautical mile = 1,852 meters (used in aviation and maritime navigation)
- 1 light-year ≈ 9.461 × 10¹⁵ meters (distance light travels in one year)
Practical Applications
Engineers and architects working with international teams need to convert between metric and imperial units daily. Runners and cyclists often need to convert kilometers to miles for race distances. Scientists use meters as the SI base unit, while astronomers prefer light-years or parsecs for cosmic distances. Our converter handles all these scales in a single tool.
Nautical Miles Explained
A nautical mile is defined as exactly 1,852 meters and corresponds to one minute of arc of latitude on Earth's surface. This makes it uniquely convenient for navigation, which is why aviation and maritime industries worldwide use nautical miles and knots (nautical miles per hour) as standard units.