Length Converter
Convert any length unit to another with this free length converter. It supports 12 units including meters, kilometers, centimeters, millimeters, micrometers, nanometers, and more. Pick a conversion below for a dedicated calculator, formula, and reference table. For example, 1 m = 0.001 km.
All length conversions
Meter → KilometerMeter → CentimeterMeter → MillimeterMeter → MicrometerMeter → NanometerMeter → MileMeter → YardMeter → FootMeter → InchMeter → Nautical MileMeter → Light YearKilometer → MeterKilometer → CentimeterKilometer → MillimeterKilometer → MicrometerKilometer → NanometerKilometer → MileKilometer → YardKilometer → FootKilometer → InchKilometer → Nautical MileKilometer → Light YearCentimeter → MeterCentimeter → KilometerCentimeter → MillimeterCentimeter → MicrometerCentimeter → NanometerCentimeter → MileCentimeter → YardCentimeter → FootCentimeter → InchCentimeter → Nautical MileCentimeter → Light YearMillimeter → MeterMillimeter → KilometerMillimeter → CentimeterMillimeter → MicrometerMillimeter → NanometerMillimeter → MileMillimeter → YardMillimeter → FootMillimeter → InchMillimeter → Nautical MileMillimeter → Light YearMicrometer → MeterMicrometer → KilometerMicrometer → CentimeterMicrometer → MillimeterMicrometer → NanometerMicrometer → MileMicrometer → YardMicrometer → FootMicrometer → InchMicrometer → Nautical MileMicrometer → Light YearNanometer → MeterNanometer → KilometerNanometer → CentimeterNanometer → MillimeterNanometer → MicrometerNanometer → MileNanometer → YardNanometer → FootNanometer → InchNanometer → Nautical MileNanometer → Light YearMile → MeterMile → KilometerMile → CentimeterMile → MillimeterMile → MicrometerMile → NanometerMile → YardMile → FootMile → InchMile → Nautical MileMile → Light YearYard → MeterYard → KilometerYard → CentimeterYard → MillimeterYard → MicrometerYard → NanometerYard → MileYard → FootYard → InchYard → Nautical MileYard → Light YearFoot → MeterFoot → KilometerFoot → CentimeterFoot → MillimeterFoot → MicrometerFoot → NanometerFoot → MileFoot → YardFoot → InchFoot → Nautical MileFoot → Light YearInch → MeterInch → KilometerInch → CentimeterInch → MillimeterInch → MicrometerInch → NanometerInch → MileInch → YardInch → FootInch → Nautical MileInch → Light YearNautical Mile → MeterNautical Mile → KilometerNautical Mile → CentimeterNautical Mile → MillimeterNautical Mile → MicrometerNautical Mile → NanometerNautical Mile → MileNautical Mile → YardNautical Mile → FootNautical Mile → InchNautical Mile → Light YearLight Year → MeterLight Year → KilometerLight Year → CentimeterLight Year → MillimeterLight Year → MicrometerLight Year → NanometerLight Year → MileLight Year → YardLight Year → FootLight Year → InchLight Year → Nautical Mile
About these units
Meter (m)
- Definition
- The meter (m) is the SI base unit of length, defined as the distance light travels in a vacuum in 1/299,792,458 of a second.
- History
- Introduced in France in 1793 as one ten-millionth of the distance from the equator to the North Pole, it was later fixed by a platinum bar and, since 1983, by the speed of light.
- Current use
- The meter is the standard unit of length in nearly every country and underpins science, engineering, construction, and sport worldwide.
Kilometer (km)
- Definition
- A kilometer (km) is 1,000 meters and is the metric unit used for measuring longer distances such as roads and travel.
- History
- It entered use with the metric system in the 1790s, combining the SI prefix "kilo-" (thousand) with the meter.
- Current use
- Most of the world expresses road distances and speed limits in kilometers; the main exceptions are the United States and the United Kingdom, which still use miles.
Centimeter (cm)
- Definition
- A centimeter (cm) is one hundredth of a meter, a convenient metric unit for everyday measurements like height and paper sizes.
- History
- It dates from the original metric system and uses the SI prefix "centi-" (one hundredth).
- Current use
- Centimeters are used for body measurements, rainfall, screen and print dimensions, and school maths across the metric world.
Millimeter (mm)
- Definition
- A millimeter (mm) is one thousandth of a meter, used where small, precise measurements are needed.
- History
- Like other metric subdivisions it was defined in the 1790s using the prefix "milli-" (one thousandth).
- Current use
- Engineers, machinists, and manufacturers specify tolerances in millimeters, and rainfall is commonly reported in mm.
Micrometer (µm)
- Definition
- A micrometer or micron (µm) is one millionth of a meter, used to measure microscopic objects.
- History
- The term "micron" was officially adopted in 1879 and renamed micrometer by the SI in 1967.
- Current use
- Micrometers describe cell sizes, bacteria, fibres, and semiconductor and optical manufacturing tolerances.
Nanometer (nm)
- Definition
- A nanometer (nm) is one billionth of a meter, the scale of atoms, molecules, and wavelengths of light.
- History
- It combines the SI prefix "nano-" (one billionth) with the meter and became common with the rise of nanotechnology.
- Current use
- Nanometers measure the wavelengths of visible light (about 380–750 nm) and the feature sizes of modern microchips.
Mile (mi)
- Definition
- A mile (mi) is an imperial unit of length equal to exactly 1,609.344 meters, or 5,280 feet.
- History
- It descends from the Roman "mille passus" (a thousand paces) and was standardised in England in 1593 as the statute mile.
- Current use
- Miles remain the everyday unit for road distance and speed in the United States and United Kingdom.
Yard (yd)
- Definition
- A yard (yd) is an imperial unit equal to 3 feet or exactly 0.9144 meters.
- History
- Once based on the length of a man’s belt or the king’s arm, it was fixed against the meter by international agreement in 1959.
- Current use
- Yards are used in the US and UK for fabric, landscaping, and the dimensions of American football fields.
Foot (ft)
- Definition
- A foot (ft) is an imperial unit of length equal to 12 inches or exactly 0.3048 meters.
- History
- Derived from the human foot, it varied across regions until the international foot was defined in 1959.
- Current use
- Feet are widely used for height, room dimensions, and aviation altitude, especially in the US and UK.
Inch (in)
- Definition
- An inch (in) is an imperial unit of length equal to exactly 2.54 centimeters, with twelve inches making a foot.
- History
- Originally the width of a thumb, the inch was standardised to 25.4 mm internationally in 1959.
- Current use
- Inches measure screen sizes, tyre and pipe dimensions, and everyday lengths in the US and UK.
Nautical Mile (nmi)
- Definition
- A nautical mile (nmi) equals exactly 1,852 meters and corresponds to one minute of latitude along a meridian.
- History
- It was defined by its relationship to the Earth’s circumference and standardised internationally in 1929.
- Current use
- Nautical miles are used in marine and air navigation; one knot equals one nautical mile per hour.
Light Year (ly)
- Definition
- A light-year (ly) is the distance light travels in one year in a vacuum, about 9.46 trillion kilometers.
- History
- The concept arose in the 19th century as astronomers sought an intuitive way to express the vast distances between stars.
- Current use
- Light-years express distances to stars and galaxies in astronomy and popular science.
Frequently asked questions
What length units can I convert?
This length converter supports 12 units: meters, kilometers, centimeters, millimeters, micrometers, nanometers, miles, yards, feet, inches, nautical miles, light years. Select any pair below to open a dedicated converter with a formula and conversion table.
How accurate is the length converter?
Conversions use exact definitional factors, so results are accurate to the precision you need for science, engineering, and everyday use. Values are rounded only for display.
Is the length converter free?
Yes. Every length conversion is completely free, needs no sign-up, and runs entirely in your browser — your inputs never leave your device.
Free, private, and instant — every conversion runs in your browser.
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