Converter category
Length Converter
Convert metric, Imperial, nautical, astronomical, typographic, historical, and scientific distance units including all SI prefixes from attometers to exameters, parsecs, Planck length, and cosmic scales.
Universal Length Converter
About length conversions
Length is one of the most common measurements people convert every day. Whether you are buying furniture, following a recipe from another country, reading a map, or working on a school science project, you will often need to switch between metric and Imperial length units. Our free length converter handles everything from tiny nanometers and micrometers to everyday millimeters, centimeters, meters, and kilometers, plus inches, feet, yards, miles, and nautical miles. It also includes specialized units used in surveying, printing, astronomy, and historical contexts. Every conversion uses exact, internationally recognized definitions, so engineers, students, travelers, and DIYers can trust the result.
Most popular length conversions
Available units
Popular length conversions (89 total)
Unit definitions
Nanometer (nm)
A nanometer is one billionth of a meter. About 100,000 times smaller than a human hair.
Origin: Used in nanotechnology, quantum physics, and molecular biology.
Current use: Nanotechnology, Semiconductor processes, DNA measurements
Picometer (pm)
1 pm = 10^-12 m, used for atomic scales.
Origin: Metric prefix pico- = 10^-12.
Current use: Atomic physics, Chemistry, Nuclear scales
Micrometer (µm)
A micrometer is one millionth of a meter, smaller than a human hair width.
Origin: From the Greek mikros meaning small. Used in microscopy and semiconductor manufacturing.
Current use: Microscopy, Semiconductor manufacturing, Filter ratings
Millimeter (mm)
A millimeter is one thousandth of a meter, about the thickness of a credit card.
Origin: Part of the metric system where milli- denotes one-thousandth.
Current use: Engineering tolerances, Rainfall measurements, Machine tooling
Centimeter (cm)
A centimeter is one hundredth of a meter. A centimeter is roughly the width of a fingernail.
Origin: The metric system originated in France in 1799. The centimeter was defined as 1/100 of a meter.
Current use: Measuring small objects, Ruler markings, DIY projects
Decimeter (dm)
1 dm = 0.1 m, about the width of a smartphone.
Origin: Metric prefix deci- = 0.1.
Current use: Everyday measurement, Small objects, Metric education
Meter (m)
The meter is the SI base unit of length. One meter equals approximately 3.28 feet or 39.37 inches.
Origin: Originally defined as one ten-millionth of the distance from the equator to the North Pole. Now defined by the speed of light: the distance light travels in 1/299,792,458 of a second.
Current use: Construction, athletics (track events), Scientific measurements
Dekameter (dam)
1 dam = 10 m, about half a bowling lane.
Origin: Metric prefix deca- = 10.
Current use: Large objects, Rare usage, Education
Hectometer (hm)
1 hm = 100 m, rarely used.
Origin: Metric prefix hecto- = 100.
Current use: Large areas, Athletics, Rare usage
Kilometer (km)
A kilometer is 1000 meters, approximately 0.621 miles. It is the standard unit for road distances in most countries.
Origin: Part of the metric system developed during the French Revolution.
Current use: Road distances, Map scales, Running events
Megameter (Mm)
1 Mm = 1000 km. Earth's diameter ≈ 12.7 Mm.
Origin: Metric prefix mega- = 10^6.
Current use: Earth diameter, Large distances, Planetary science
Gigameter (Gm)
1 Gm = 1 million km.
Origin: Metric prefix giga- = 10^9.
Current use: Spacecraft distances, Earth-Moon space, Astronomy
Terameter (Tm)
1 Tm = 1 trillion meters.
Origin: Metric prefix tera- = 10^12.
Current use: Solar system distances, Astronomy research
Petameter (Pm)
1 Pm = about 6.7 astronomical units.
Origin: Metric prefix peta- = 10^15.
Current use: Outer solar system, Interplanetary distances
Exameter (Em)
1 Em = about 105.7 light-years.
Origin: Metric prefix exa- = 10^18.
Current use: Stellar distances, Galaxy scales
Inch (in)
An inch is exactly 2.54 centimeters. It is roughly the length of the top segment of a thumb.
Origin: The inch was historically defined as the width of a man's thumb. King Edward II of England defined it as three barleycorns end-to-end in 1324.
Current use: Screen sizes, Pipe diameters, Woodworking
Foot (ft)
A foot is exactly 12 inches or 30.48 centimeters. It is commonly used for measuring height and short distances.
Origin: Used throughout history with varying lengths. The modern foot was standardized in 1959 as exactly 30.48 cm.
Current use: Height measurement, Room dimensions, Real estate
Yard (yd)
A yard is exactly 3 feet or 36 inches. It is commonly used in sports and fabric measurements.
Origin: The yard was standardized in the 13th century by King Henry I of England as the distance from his nose to his outstretched thumb.
Current use: American football, Fabric sales, Gardening
Mile (mi)
A statute mile is exactly 1760 yards or 1609.344 meters. It is used for road distances in the US and UK.
Origin: Derived from the Roman mille passuum (thousand paces). A pace was two steps of about 5 feet.
Current use: Road distances in US/UK, Speed limits, Marathon distance
Nautical Mile (nmi)
A nautical mile is based on the circumference of Earth, equal to one minute of latitude. It is used in aviation and maritime navigation.
Origin: Developed for maritime and aerial navigation based on the Earth's geometry.
Current use: Shipping, Aviation, Marine navigation
Furlong (fur)
A furlong is 1/8 mile or 220 yards, traditionally used in agriculture.
Origin: From Old English furh (furrow) and lang (long).
Current use: Agriculture, Horse racing, Historical land
Chain (ch)
A chain is 66 feet or 4 rods, used in surveying.
Origin: Invented by Edmund Gunter in 1620.
Current use: Surveying, Land records, Cricket pitch
Rod (rd)
A rod is 16.5 feet or 5.5 yards. Also called a pole or perch.
Origin: Ancient unit used in agriculture.
Current use: Agriculture, Boundary markers, Fencing
Statute League (lea)
A league is 3 miles, an old travel distance.
Origin: Ancient Roman unit, about the distance one can walk in an hour.
Current use: Historical travel, Literature, Land measurement
Astronomical Unit (AU)
1 AU = Earth-Sun distance ≈ 150 million km.
Origin: Defined as the Earth's orbital semi-major axis.
Current use: Astronomy, Planetary distances, Solar system
Light-year (ly)
Light travels 1 ly in 1 year ≈ 9.46 trillion km.
Origin: Used in astronomy for vast distances.
Current use: Astronomy, Space distances, Stellar measurement
Parsec (pc)
1 parsec ≈ 3.26 light-years. From parallax second.
Origin: Derived from stellar parallax.
Current use: Astronomy, Interstellar distances, Galactic scale
Kiloparsec (kpc)
1 kpc = 1000 parsecs ≈ 3262 light-years.
Origin: Astronomical unit.
Current use: Galaxy structure, Stellar astronomy
Megaparsec (Mpc)
1 Mpc = 1 million parsecs.
Origin: Astronomical unit.
Current use: Extragalactic astronomy, Cosmology
Femtometer (fm)
1 fm = 10^-15 m, same as a fermi.
Origin: Named after Enrico Fermi.
Current use: Nuclear physics, Particle physics, Quarks
Attometer (am)
1 am = 10^-18 m, quark-scale distances.
Origin: Metric prefix atto- = 10^-18.
Current use: Particle physics, Quark studies, Fundamental physics
Angstrom (Å)
1 Å = 10^-10 m, atomic scale. Used for wavelengths.
Origin: Named after Anders Ångström.
Current use: Atomic physics, Chemistry bonds, Crystallography
Bohr Radius (a₀)
Bohr radius ≈ 5.29×10^-11 m, electron orbital radius.
Origin: From Niels Bohr's atomic model.
Current use: Atomic physics, Quantum mechanics, Spectroscopy
X-unit (X)
X-unit ≈ 1.002×10^-13 m, used for X-ray wavelengths.
Origin: Defined by Siegbahn.
Current use: X-ray crystallography, spectroscopy
Fermi (F)
1 fermi = 10^-15 m, same as femtometer.
Origin: Named after Enrico Fermi.
Current use: Nuclear physics, Particle physics
Planck Length (ℓP)
Planck length ≈ 1.6×10^-35 m, smallest measurable length.
Origin: From Planck constant calculations.
Current use: Quantum gravity, String theory, Theoretical physics
Electron Radius (re)
Classical electron radius ≈ 2.8×10^-15 m.
Origin: Classical physics calculation.
Current use: Particle physics, Electron scattering
Nautical Mile (UK) (NM (UK))
UK nautical mile = 1853.184 m, slightly longer than international.
Origin: British Admiralty standard.
Current use: UK shipping, Historical navigation
Nautical League (Int.) (nlg)
International nautical league = 3 nautical miles.
Origin: Sea league at sea.
Current use: Marine navigation, Sea distances
Nautical League (UK) (nlg (UK))
UK nautical league = 5559.552 m.
Origin: British sea league.
Current use: UK maritime, Historical navigation
Statute League (lea (st))
Statute league = 3 statute miles.
Origin: Common law league.
Current use: Historical land, Literature
Mile (Statute) (mi (st))
Standard US/UK mile = 1760 yards.
Origin: Standardized in 1592.
Current use: Land measurement, Road distances
Mile (Roman) (mi (Roman))
Roman mile = 1000 paces (mille passus).
Origin: Ancient Roman unit.
Current use: Historical measurements, Roman archaeology
Kiloyard (kyd)
1 kiloyard = 1000 yards = 3000 feet.
Origin: Engineering unit.
Current use: Construction, Engineering (US)
Furlong (US Survey) (fur (US))
US survey furlong = 201.168 m.
Origin: US survey foot standard.
Current use: US surveying, Cadastral measurements
Chain (US Survey) (ch (US))
US survey chain = 20.117 m.
Origin: US survey standard.
Current use: US land survey, Cadastral
Rope (rope)
1 rope = 20 feet.
Origin: British unit for measuring rope.
Current use: Rope measurement, Historical
Rod (US Survey) (rd (US))
US survey rod = 5.029 m.
Origin: US survey standard.
Current use: US surveying, Boundaries
Fathom (fath)
1 fathom = 6 feet, used for measuring depth.
Origin: From Old English fæthm (armspan).
Current use: Nautical depth, Maritime, Rope length
Fathom (US Survey) (fath (US))
US survey fathom = 1.829 m.
Origin: US survey standard.
Current use: US nautical survey
Ell (ell)
1 ell = 45 inches, cloth measure.
Origin: From Latin ulna (elbow).
Current use: Cloth measurement, Textiles
Foot (US Survey) (ft (US))
US survey foot = 1200/3937 m ≈ 0.3048 m.
Origin: US survey standard.
Current use: US land survey, Cadastral maps
Link (li)
1 link = 1/100 chain = 7.92 inches.
Origin: Gunter's chain subdivision.
Current use: Surveying, Land measurement
Link (US Survey) (li (US))
US survey link = 0.201 m.
Origin: US survey standard.
Current use: US surveying
Cubit (UK) (cubit)
1 cubit = 18 inches, ancient Egyptian.
Origin: From elbow to fingertips.
Current use: Historical measurement, Archaeology
Hand (hand)
1 hand = 4 inches, used for horse height.
Origin: Width of a hand.
Current use: Horse measurement, Livestock height
Span (Cloth) (span)
1 span = 9 inches, distance thumb to little finger.
Origin: From hand spread.
Current use: Cloth measurement, Historical
Finger (Cloth) (finger)
1 finger = 4.5 inches.
Origin: Cloth measurement.
Current use: Textiles, Historical clothing
Nail (Cloth) (nail)
1 nail = 2.25 inches, cloth unit.
Origin: From nail of finger.
Current use: Cloth selling, Historical
Inch (US Survey) (in (US))
US survey inch = 100/3937 m.
Origin: US survey standard.
Current use: US land survey
Barleycorn (barleycorn)
1 barleycorn = 1/3 inch, old seed unit.
Origin: From length of a barleycorn.
Current use: Historical, Shoe sizes (UK)
Mil (Thou) (mil)
1 mil = 1/1000 inch, for wire thickness.
Origin: Military term.
Current use: Wire gauge, Manufacturing, Electronics
Microinch (µin)
1 microinch = 10^-6 inch.
Origin: Precision engineering.
Current use: Machining, Optics, Semiconductors
Bohr Radius (a.u.) (a.u.)
Atomic unit of length = Bohr radius.
Origin: Atomic unit.
Current use: Atomic physics, Quantum chemistry
Pica (pica)
1 pica = 1/6 inch, typography unit.
Origin: From French pica (magpie).
Current use: Typography, Desktop publishing, Print
Point (pt)
1 point = 1/72 inch, font size unit.
Origin: Printers' point system.
Current use: Typography, Fonts, Publishing
Twip (twip)
1 twip = 1/1440 inch, typography.
Origin: Twentieth of a point.
Current use: Typography, DTP, Microsoft Word
Aln (aln)
An aln is a historical Scandinavian unit of length, about 59 cm.
Origin: Used in Scandinavia for cloth measurement.
Current use: Historical Scandinavia, Cloth measurement
Famn (famn)
A famn is a historical Scandinavian unit of length, about 1.78 m.
Origin: Old Norse unit from finger tip to elbow.
Current use: Historical Scandinavia, Land measurement
Caliber (cl)
1 caliber = 0.01 inch = 0.254 mm. Used for gun bore diameters.
Origin: From Arabic qalib (mold).
Current use: Firearms, Ammunition, Weapons manufacturing
Centiinch (cin)
1 centiinch = 0.01 inch = 0.254 mm.
Origin: Rare Imperial unit.
Current use: Precision engineering, Historical
Ken (ken)
A ken is a Japanese unit of length, about 1.82 m.
Origin: Traditional Japanese unit.
Current use: Japanese architecture, Historical measurement
Russian Archin (archin)
A Russian archin is about 0.711 m.
Origin: Old Russian unit from the 16th century.
Current use: Russian history, Cloth measurement
Roman Actus (actus)
A Roman actus is about 35.5 m.
Origin: Roman unit of length.
Current use: Roman history, Land measurement
Vara de Tarea (vara)
A vara de tarea is about 2.5 m, used in Spanish-speaking regions.
Origin: Spanish colonial unit.
Current use: Latin American land, Spanish surveying
Vara Conuquera (vara c.)
A vara conuquera is about 2.5 m.
Origin: Spanish unit.
Current use: Spanish surveying, Historical
Vara Castellana (vara ca.)
A vara castellana is about 0.835 m.
Origin: Castilian unit.
Current use: Spanish history, Land measurement
Cubit (Greek) (cubit (Gr))
A Greek cubit is about 0.463 m.
Origin: Ancient Greek unit.
Current use: Ancient Greece, Archaeology
Long Reed (long reed)
A long reed is about 3.2 m.
Origin: Biblical unit of measurement.
Current use: Biblical measurement, Historical
Reed (reed)
A reed is about 2.74 m.
Origin: Ancient measuring unit.
Current use: Historical measurement, Biblical
Long Cubit (long cubit)
A long cubit is about 0.533 m (7 palms).
Origin: Ancient Near Eastern unit.
Current use: Biblical measurement, Archaeology
Handbreadth (h.breadth)
A handbreadth is about 7.62 cm.
Origin: Ancient unit.
Current use: Historical measurement
Fingerbreadth (f.breadth)
A fingerbreadth is about 1.9 cm.
Origin: Ancient unit.
Current use: Historical measurement
Arpent (arpent)
An arpent is about 58.5 m. Used in French Canada.
Origin: French surveying unit.
Current use: French Canada, Historical surveying
Earth Equatorial Radius (R⊕)
Earth's equatorial radius ≈ 6378 km.
Origin: Geodetic standard.
Current use: Geodesy, Astronomy, Satellite orbits
Earth Polar Radius (R⊕ (polar))
Earth's polar radius ≈ 6357 km.
Origin: Geodetic standard.
Current use: Geodesy, Mapping, Science
Earth–Sun Distance (AU (earth))
Earth-Sun distance ≈ 1 AU ≈ 150 million km.
Origin: Astronomical standard.
Current use: Astronomy, Solar system
Sun's Radius (R☉)
Sun's radius ≈ 696,000 km.
Origin: Solar standard.
Current use: Astronomy, Solar physics
Common uses for length conversions
Length conversions are essential for construction, interior design, travel planning, international shopping, running and fitness tracking, engineering drawings, and education.
Frequently asked questions about length
How do you convert meters to feet?+
Multiply the length in meters by 3.28084. For example, 2 meters is about 6.56 feet. Our converter does this instantly and shows the exact formula.
What is the difference between metric and Imperial length units?+
Metric units such as meters and kilometers are based on powers of ten and are used in most countries. Imperial units such as inches, feet, yards, and miles are mainly used in the United States and a few other places.
Which length units does this converter support?+
It supports metric, Imperial, US survey, nautical, astronomical, printing, and historical units — over 70 in total.