Length Converter
Convert length units instantly—millimeters (mm), centimeters (cm), meters (m), kilometers (km), inches (in), feet (ft), yards (yd), and miles (mi). Enter a value, choose units, and get accurate results in seconds. Free, fast, and easy to use.
Length Converter
The Length Converter converts between 31 length and distance units spanning seven categories: metric SI (picometer through kilometer), imperial and US customary (mil through statute mile), three nautical mile definitions, typography units (point, pica, em), astronomical and scientific units (angstrom through parsec), and historical units (furlong, fathom, rod, ell, league). Select the From and To units, enter the value, and click Convert.
Length is the most frequently converted physical quantity, appearing in construction, travel, manufacturing, screen specifications, navigation, typography, and astronomy. The 31-unit range of this converter covers both the most common everyday conversions (meters to feet, kilometers to miles, inches to centimeters) and the specialized units encountered in specific industries and disciplines.
How to use the Length Converter
- Enter the length value to convert.
- Select the From unit — the unit your value is currently in.
- Select the To unit — the unit you want to convert to.
- Click Convert. The result appears immediately.
- To convert to additional units, change the To dropdown and click Convert again without re-entering the value.
All 31 units — conversion factors and contexts
The table below covers all 31 supported units with their meter equivalent and the context in which each is typically used, organized by category:
| Unit | In meters (m) | Typical context |
| Metric / SI units | ||
| Picometer (pm) | 1e-12 m | Atomic bond lengths and ionic radii in chemistry. The carbon-carbon single bond is approximately 154 pm. X-ray wavelengths are typically 0.01–10 nm (10–10,000 pm). |
| Nanometer (nm) | 1e-9 m | Semiconductor feature sizes, optical wavelengths, virus sizes, and nanotechnology. Visible light is 380–700 nm. Modern CPU process nodes are stated in nm (e.g. 3 nm, 5 nm nodes). |
| Micrometer (µm) | 1e-6 m | Bacteria sizes, human hair diameter (~70 µm), machining tolerances in precision engineering, wavelengths of infrared light. Also called a micron. |
| Millimeter (mm) | 0.001 m | Small manufactured parts, rainfall measurements, screw thread dimensions, medical imaging (tumor sizes), product dimensions. |
| Centimeter (cm) | 0.01 m | Human body measurements, clothing sizes, screen sizes (diagonal), small household objects. 1 cm = 10 mm. |
| Decimeter (dm) | 0.1 m | Rarely used in everyday contexts but appears in some European educational systems and older scientific literature. 1 dm = 10 cm. |
| Meter (m) | 1 m | The SI base unit of length. Room dimensions, building heights, fabric lengths, running distances, wavelengths of radio waves. |
| Kilometer (km) | 1,000 m | Road distances, city separations, mountain heights, map scales, marathon distances (42.195 km). Standard distance unit in metric countries for travel and geography. |
| Imperial / US customary units | ||
| Mil (thou) | 0.0000254 m | US engineering and manufacturing: wire thickness, film thickness, coating thickness. 1 mil = 0.001 inch = 25.4 micrometers. Not to be confused with millimeter (mm) — a mil is roughly 1/40th of a millimeter. |
| Caliber (cal) | 0.000254 m | Firearm barrel and projectile diameter. 1 caliber = 0.01 inch = 0.254 mm. A .308 caliber rifle fires a projectile with diameter 0.308 inches = 7.82 mm. Caliber is also used for dimensioning in some precision engineering contexts. |
| Inch (in) | 0.0254 m | Product dimensions, screen sizes (diagonal), human body measurements in US/UK, plumbing pipe sizes. 1 inch = 2.54 cm exactly. 12 inches = 1 foot. |
| Foot (ft) | 0.3048 m | Height (US/UK), aircraft altitude (universal in aviation), building floor heights, well and borehole depths. 1 ft = 12 in = 30.48 cm. 3 feet = 1 yard. |
| Yard (yd) | 0.9144 m | Fabric measurements in the US, sports field dimensions (American football), golf distances, some construction measurements. 1 yd = 3 ft = 36 in = 0.9144 m. |
| Rod (rd) | 5.0292 m | Historical US/UK land surveying unit. 1 rod = 16.5 feet = 5.5 yards. Also called a pole or perch. Still used in some US and UK land descriptions and surveyors' records. 1 acre = 160 square rods. |
| Fathom | 1.8288 m | Water depth measurement in maritime and nautical contexts. 1 fathom = 6 feet = 1.8288 m. Sea charts and depth soundings still use fathoms in some contexts, particularly UK Admiralty charts. |
| Furlong | 201.168 m | Horse racing distances (a standard flat race in the UK is 5–12 furlongs). 1 furlong = 220 yards = 1/8 mile = 201.168 m. Also used in some agricultural land descriptions. |
| Ell | 1.143 m (English ell) | A historical textile measurement unit. The English ell = 45 inches = 1.143 m. The Scottish ell (37 inches) and Flemish ell (27 inches) are different values for the same unit name. Still occasionally encountered in historic textile records and historic building surveys. |
| Mile (US statute) | 1,609.344 m | The standard mile used for road distances, speed limits, and geographic distances in the United States. 1 statute mile = 5,280 feet = 1,760 yards = 1,609.344 m. The most common meaning of 'mile' in everyday US usage. |
| Nautical miles — three distinct definitions | ||
| Mile (international nautical) | 1,852 m | The current international standard nautical mile: exactly 1,852 meters. Used for maritime navigation, aviation (where it is called the nautical mile or nmi), and international maritime law. 1 knot = 1 international nautical mile per hour. |
| Mile (UK nautical) | 1,853.18 m | The former British Admiralty nautical mile, approximately 1,853.18 meters (6,080 feet). Defined as the length of 1 minute of arc of latitude at 48°N (the mean latitude of the English Channel). Largely replaced by the international nautical mile. |
| Mile (US nautical) | 1,853.25 m | The former US nautical mile, approximately 1,853.25 meters (6,080.2 feet). Used by the US before 1954, when both the US and UK adopted the international nautical mile definition. |
| Typography units | ||
| Point (pt) | 0.000353 m | Typography and print design: font sizes, line spacing, border widths. 1 point = 1/72 inch (PostScript/CSS definition, now universal) = 0.353 mm. Font size '12pt' means the font body is 12/72 inch tall. Points are the base unit for type in print design software (InDesign, Illustrator, QuarkXPress) and CSS. |
| Pica (printer's) | 0.00423 m | Typography: column widths, margins, and large text measurements in print design. 1 pica = 12 points = 1/6 inch = 4.233 mm. Used in page layout for specifying column widths and text block dimensions. |
| Em | varies (relative) | Typography: a relative unit equal to the current font size. In a 16px document, 1 em = 16px. Used primarily in CSS and digital typography for relative sizing (padding, margin, font-size). In metal typesetting, 1 em was the width of the capital letter M in the current typeface. Does not have a fixed physical dimension. |
| Scientific and astronomical units | ||
| Angstrom (A) | 1e-10 m | Atomic-scale measurements in chemistry and crystallography. 1 angstrom = 0.1 nanometer = 10^-10 m. Water molecule diameter ~2.75 A. Typical atomic bond length 1–3 A. Still widely used in spectroscopy and crystallography despite not being an SI unit. |
| Fermi (fm) | 1e-15 m | Nuclear physics: the scale of atomic nuclei. 1 fermi = 1 femtometer = 10^-15 m. The proton has a radius of approximately 0.87 fm. Used in nuclear physics and high-energy physics for particle sizes. |
| Astronomical Unit (AU) | 1.496e+11 m | Solar system distances. 1 AU = the mean distance from Earth to the Sun = approximately 149.6 million km = 93 million miles. Mars is approximately 1.52 AU from the Sun; Jupiter 5.2 AU; Neptune 30 AU. |
| Light Year (LY) | 9.461e+15 m | Interstellar distances. 1 light year = the distance light travels in one year in a vacuum = approximately 9.461 trillion km = 63,241 AU. Proxima Centauri (nearest star to the Sun) is 4.24 light years away. The Milky Way galaxy is approximately 100,000 light years in diameter. |
| Parsec (pc) | 3.086e+16 m | Professional astronomy: stellar and galactic distances. 1 parsec = approximately 3.26 light years = 206,265 AU. Defined as the distance at which 1 AU subtends an angle of 1 arcsecond. Proxima Centauri is 1.30 parsecs away. Galactic distances are often stated in kiloparsecs (kpc) or megaparsecs (Mpc). |
| Leagues | ||
| League (UK) | 4,828.032 m | The traditional English league = 3 statute miles = 4,828 m. A historical unit of walking distance — approximately one hour's walk. Used in classic literature ('Twenty Thousand Leagues Under the Sea') and some historic land descriptions. Rarely used in modern contexts. |
| League (int'l) | 5,556 m | The international nautical league = 3 international nautical miles = 5,556 m. Used historically in maritime navigation for distances. Largely obsolete in modern navigation. |
The mil and millimeter are easily confused — they look similar in abbreviation and the names both start with 'mil'. A mil (also called a thou) = 0.001 inch = 0.0254 mm. A millimeter = 0.001 meter = 1,000 micrometers. The mil is approximately 1/40th of a millimeter. Mil is a US manufacturing and engineering unit; millimeter is the metric unit. When a US engineering datasheet specifies a coating thickness of '3 mils', it means 76.2 micrometers (0.0762 mm) — not 3 millimeters.
Common use cases by context
| Context | Common conversion | Notes |
| Construction and building | mm ↔ inches, m ↔ ft | Architectural drawings may be in metric (mm, m) or imperial (inches, feet) depending on country. 1 inch = 25.4 mm; 1 foot = 304.8 mm; 1 meter = 3.281 feet. When working from imported plans, always convert all dimensions to the same unit system before calculating materials. |
| Travel and navigation | km ↔ miles | Speed limits, road signs, and distances in the US and UK are in miles; most other countries use kilometers. 1 mile = 1.609 km; 1 km = 0.621 miles. A 100 km/h speed limit = 62.1 mph. Quick approximation: km x 0.62 = miles; miles x 1.61 = km. |
| Screen and product sizes | inches ↔ cm ↔ mm | Screen diagonal sizes are universally stated in inches (a 27-inch monitor, 65-inch TV). Physical dimensions of devices may be in mm (metric markets) or inches (US market). 1 inch = 25.4 mm = 2.54 cm. |
| Maritime and aviation | nautical miles ↔ km ↔ statute miles | Aviation uses nautical miles (nmi) and knots worldwide. Maritime navigation uses nautical miles. Road distance uses statute miles (US) or km. 1 international nautical mile = 1.852 km = 1.151 statute miles. Aircraft altitude is universally in feet, even in countries that use metric for ground distances. |
| Typography and web design | points ↔ mm ↔ px | Print design uses points (pt) and picas. Web design uses px and em. 1 pt = 1/72 inch = 0.353 mm. At 96 dpi (standard screen resolution), 1 pt ≈ 1.33 px. CSS uses px, em, rem, pt, and cm as length units. |
| Scientific research | nm ↔ A ↔ pm, AU ↔ LY ↔ pc | Spectroscopy and chemistry use nm and angstroms. Nuclear physics uses fm (fermi). Astronomy uses AU (solar system), light years (popular science), and parsecs (professional astronomy). Convert to SI units (meters) for calculations requiring consistent units. |
Three nautical miles — which one to use
The converter includes three nautical mile definitions: international, UK (Admiralty), and US. For all modern navigation, aviation, and maritime use, the international nautical mile (1,852 m exactly) is the correct choice. The UK and US nautical miles are historical definitions that were replaced by the international standard in 1954 (UK) and were never used after the US adopted the international standard. They appear in the converter for completeness and for converting historical documents and charts.
In aviation and maritime contexts, 'nautical mile' always means the international nautical mile: 1,852 meters exactly. One knot = one international nautical mile per hour. Aircraft speeds, shipping distances, exclusion zones, and all current maritime charts use the international definition. The UK Admiralty nautical mile (6,080 feet = 1,853.18 m) and US nautical mile (6,080.2 feet = 1,853.25 m) are encountered only in pre-1954 charts, historical texts, and older navigation instruments.
Usage limits
| Account type | Daily conversions |
| Guest | 25 per day |
| Registered | 100 per day |
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Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54 centimeters = 1 inch. This is a defined value, not an approximation — the international inch was defined as exactly 25.4 mm in 1959. To convert inches to centimeters: multiply by 2.54. To convert centimeters to inches: divide by 2.54. Examples: 6 inches = 15.24 cm; 30 cm = 11.81 inches. For a quick mental estimate, 1 inch is approximately 2.5 cm; 10 cm is approximately 4 inches.
How do I convert kilometers to miles?
Multiply kilometers by 0.621371 to get statute miles. To convert miles to kilometers: multiply by 1.609344. Examples: 100 km = 62.14 miles; 60 mph = 96.56 km/h. Quick approximation: multiply km by 0.6 for a rough miles estimate; multiply miles by 1.6 for a rough km estimate. The Fibonacci sequence gives a useful approximation: consecutive Fibonacci numbers (5/8, 8/13, 13/21, 21/34) approximate the km/mile ratio (0.625 ≈ 0.621).
How do I convert feet to meters?
Multiply feet by 0.3048 to get meters. To convert meters to feet: multiply by 3.28084. Examples: 6 feet = 1.8288 m; 100 meters = 328.08 feet. In everyday use: 1 foot ≈ 30 cm; 1 meter ≈ 3.28 feet ≈ 3 feet 3 inches. A person 5 feet 10 inches tall is 5.833 feet = 177.8 cm = 1.778 meters. Note that aircraft altitude is stated in feet universally — a flight level of FL350 means 35,000 feet (approximately 10,668 m).
What is the difference between a statute mile and a nautical mile?
A statute mile (US mile) = 5,280 feet = 1,609.344 meters. It is the mile used for road distances and speed limits in the US and UK. A nautical mile (international) = exactly 1,852 meters = 6,076.1 feet. It is used in aviation and maritime navigation globally. 1 nautical mile is approximately 1.151 statute miles; 1 statute mile is approximately 0.869 nautical miles. The nautical mile is defined based on the Earth's geometry — it equals 1 minute of arc of latitude.
What are points and picas in typography?
Points (pt) and picas are typographic length units used in print design. 1 point = 1/72 inch = 0.353 mm (PostScript/CSS standard). Font sizes are stated in points — 12pt text means the font body is 12/72 inch tall. 1 pica = 12 points = 1/6 inch = 4.233 mm. Picas are used for column widths, margins, and text block sizes in page layout. In digital design and CSS, points and pixels are both used: at standard 96 dpi screen resolution, 1 point = approximately 1.333 pixels.
What is an angstrom and where is it used?
An angstrom (symbol A) = 10^-10 meters = 0.1 nanometers. It is used in chemistry, crystallography, and spectroscopy to describe atomic-scale distances: atomic bond lengths (typically 1–3 A), atomic radii (0.5–2 A), and molecular dimensions. It is not an SI unit (the SI unit for this scale is the nanometer) but remains widely used in crystallography and materials science. The visible light spectrum is typically described as 380–700 nm, which is equivalent to 3,800–7,000 A.
How far is a light year in kilometers?
1 light year = approximately 9.461 trillion kilometers (9.461 x 10^12 km) = 5.879 trillion statute miles. It is the distance light travels in one vacuum year at the speed of light (approximately 299,792 km/s). Light years are used to describe interstellar distances in popular science. Proxima Centauri, the nearest star to the Sun, is 4.24 light years = approximately 40 trillion km away. Professional astronomers prefer parsecs: 1 parsec = 3.26 light years = approximately 30.9 trillion km.
Is the Length Converter free?
Yes. The converter is free within the daily usage limits shown above. Guest users can perform 25 conversions per day without creating an account. Registering a free ToolsPiNG account increases the daily limit to 100 conversions per day.