Choose the unit you are converting from — mm, cm, m, km, in, ft, yd, mile, nautical mile, micrometer, nanometer, furlong, fathom, or light-year.
Choose the unit you want the answer in. The conversion is bidirectional — swap anytime.
Type any positive or negative number. The primary result updates instantly.
Common equivalents in meters, feet, inches, kilometers, miles, and yards are displayed below so you can cross-reference at a glance.
Every length unit is converted through meters as the base. The value is first multiplied by the FROM factor to get meters, then divided by the TO factor to obtain the result. This keeps conversions consistent and bidirectional.
meters = value × factor(from) | result = meters / factor(to)
1 inch = 2.54 cm exactly — this is the international inch definition
1 foot = 12 inches = 0.3048 m — use this to jump between imperial lengths
1 mile = 5,280 ft = 1.609 km — common for road-distance conversions
1 nautical mile = 1,852 m — used in aviation and marine navigation, not the same as a statute mile
1 light-year is a distance (not time) — the distance light travels in vacuum in one Julian year
Length conversion between metric and imperial systems is one of the most common unit conversion needs worldwide. The metric system, based on the meter, is used by every country except the United States, Myanmar, and Liberia for official measurement, while Americans work daily with inches, feet, yards, and miles. The key conversion factors are straightforward but easy to misremember: 1 inch equals exactly 25.4 millimeters (this is a defined, not measured, relationship since 1959), 1 foot equals 0.3048 meters, 1 mile equals 1.609344 kilometers, and 1 nautical mile equals 1.852 kilometers. In scientific and engineering contexts, SI prefixes extend the meter from nanometers (10⁻⁹ m, used in semiconductor fabrication) through micrometers (10⁻⁶ m, used in machining tolerances) up to kilometers and beyond. Astronomical distances use light-years (9.461 trillion km) or parsecs. Historical units like furlongs (220 yards, still used in horse racing) and fathoms (6 feet, still used in maritime depth) persist in specialized fields. Whether you are an engineer working with international specifications, a traveler converting road signs, or a student solving physics problems, quick and accurate length conversion prevents costly errors.
Metric units (mm, cm, m, km) are built on powers of 10 around the meter, the SI base unit. Imperial / US units (inch, foot, yard, mile) use legacy ratios: 12 in = 1 ft, 3 ft = 1 yd, 1,760 yd = 1 mi. Converting between systems uses fixed factors — 1 in = 2.54 cm, 1 ft = 0.3048 m, 1 mi = 1,609.344 m. Our length converter handles both systems bidirectionally.
Beyond everyday units, this tool supports micrometers (microns, 10⁻⁶ m) and nanometers (10⁻⁹ m) for science, furlongs (1/8 mile) and fathoms (6 ft) for historic/marine use, nautical miles (1,852 m) for aviation and navigation, and light-years (~9.461 × 10¹⁵ m) for astronomy — all converted through the meter as the common base.
Data sourced from trusted institutions
All formulas verified against official standards.