Length Converter
Convert between metres, kilometres, miles, feet, inches, yards, nautical miles, light-years, angstroms, and more — all length and distance units in one place.
All Unit ConvertersAll conversions from 1 metre
| Unit | Symbol | Value |
|---|
How the length converter scales from the Planck length to a parsec using one metre reference
Length is the unit family everyone learns first and few people realize spans forty five orders of magnitude in practical use. This tool’s table runs from the Planck length, the smallest distance physics currently treats as meaningful, up through nanometres, everyday metric and imperial units, nautical measures, and out to the light-year and parsec used in astronomy. Every one of those nineteen units is defined as an exact multiplier against a single reference: the metre.
Conversion happens entirely in the browser through simple multiplication and division against a static factor array. No location, measurement or query is ever sent off the page.
How a length conversion runs
val × 1609.344, the exact international mile definition rather than a rounded approximation.
Full unit table, factor relative to one metre
| Unit | Symbol | Factor (m) |
|---|---|---|
| Metre | m | 1 (base unit) |
| Kilometre | km | 1,000 |
| Centimetre | cm | 0.01 |
| Millimetre | mm | 0.001 |
| Micrometre | μm | 0.000001 |
| Nanometre | nm | 0.000000001 |
| Ångström | Å | 1e-10 |
| Mile | mi | 1,609.344 |
| Yard | yd | 0.9144 |
| Foot | ft | 0.3048 |
| Inch | in | 0.0254 |
| Nautical mile | nmi | 1,852 |
| Fathom | ftm | 1.8288 |
| Furlong | fur | 201.168 |
| Chain | ch | 20.1168 |
| Light-year | ly | 9.4607304725808e15 |
| Astronomical Unit | AU | 1.495978707e11 |
| Parsec | pc | 3.0856775814914e16 |
| Planck length | ℓP | 1.616255e-35 |
The scale extremes worth knowing
The astronomical end
The astronomical unit, roughly the Earth-Sun distance, anchors the light-year and parsec. A parsec, at about 3.26 light-years, is defined by parallax angle: it’s the distance at which one astronomical unit subtends an angle of exactly one arcsecond, which is why professional astronomy favors it over the more familiar light-year.
The subatomic end
The Planck length, at roughly 1.6e-35 metres, comes from combining the gravitational constant, the speed of light and the reduced Planck constant. It isn’t a unit anyone measures with directly; it marks the scale where current physics theories are expected to break down.
Where these units originate
The metre is one of the seven SI base units, currently defined by fixing the speed of light at exactly 299,792,458 metres per second. The imperial units in this table, the inch, foot, yard and mile, all trace to the 1959 international agreement between the US, UK and other Commonwealth nations that standardized the yard at exactly 0.9144 metres, which is why the factors here are clean terminating decimals rather than the messier historical values used before that treaty. The furlong and chain predate that agreement by centuries, rooted in English agricultural land measurement, and survive today mainly in horse racing distances and old cadastral surveys.
Length standard references
- BIPM SI Brochure defines the metre and its fixed relationship to the speed of light.
- NIST, SI Units documents the 1959 international yard and pound agreement behind the imperial conversion factors used here.
- International Hydrographic Organization is the body behind the 1929 international definition of the nautical mile.
- International Astronomical Union, measuring the universe explains the parallax based definition of the parsec and its relationship to the astronomical unit.
Everyday and technical length work
Converting a US construction drawing in feet and inches into metric for an international contractor, working out nautical mile distances for boat or flight planning against a road mile trip estimate, translating a materials science measurement from nanometres or ångströms into metres for a lab report, putting astronomical distances quoted in light-years into parsecs for a research paper, and checking old English land survey documents that reference furlongs or chains against a modern metric map.
Common Questions
FAQ: Length Converter
One metre equals exactly 3.28084 feet. Equivalently, 1 foot = 0.3048 metres (exact, by international definition). This means 1 metre is about 3 feet 3⅜ inches.
One mile equals exactly 1.609344 kilometres. A quick approximation: multiply miles by 1.6 to get kilometres, or multiply kilometres by 0.621 to get miles.
One centimetre = 0.393701 inches (about 0.4 inches). One inch = 2.54 cm exactly. This is the exact international definition established in 1959.
A nautical mile equals exactly 1852 metres (1.852 km or about 1.15078 statute miles). It is defined as one arcminute of latitude on Earth’s surface, making it naturally useful for navigation. Speed in nautical miles per hour is called a knot.
From the blog
Reading around units
Where measurement systems came from and why two of them still argue.
