kilometer
Lengthexact by definition
The kilometre is one thousand metres, an exact decimal prefix on the SI base unit. It is the standard unit of road distance and map scale in most countries. The factor is exact by definition.
Watch out: One kilometre is about 0.621 miles, so a speed limit of 100 km/h is roughly 62 mph. The reverse conversion, 1 mile = 1.609 km, is the one drivers most often need at a border.
| 1 | 1,000 |
About the kilometer
The kilometre is the unit of getting somewhere: road signs, race distances and map scales in nearly every country. The marathon is 42.195 km, a figure inherited from the 1908 London Olympic course and adopted as the official distance in 1921. The International Space Station orbits about 400 km up, an airliner cruises near 11 km of altitude, and the metre's own origin story means the distance around the Earth through the poles is close to 40,000 km, since the metre was built as one ten-millionth of the pole-to-equator quadrant.
Scandinavia quietly stacks a larger unit on top of it. In Sweden and Norway, road distances in conversation come in mil, the Scandinavian mile of exactly 10 km, and fuel consumption is commonly quoted in litres per mil; the road signs stay in kilometres, but ask how far Gothenburg is from Stockholm and the answer comes back as about 47 mil. On this site the kilometre feeds the distance, speed and travel-time calculations, where the factor of 3.6 between km/h and m/s does most of the work, and the mile conversion in the caution above covers the remaining border crossings.
One kilometer in every length unit
| 6.18714e+37 | Planck length (lP) | |
| 1.00000e+18 | femtometer (fm) | |
| 1.00000e+15 | picometer (pm) | |
| 18,897,300,000,000 | bohr radius (a0) | |
| 10,000,000,000,000 | angstrom (Å) | |
| 1,000,000,000,000 | nanometer (nm) | convert → |
| 1,000,000,000 | micrometer (μm) | convert → |
| 39,370,100 | thou (thou) | |
| 2,834,650 | point (pt) | |
| 1,000,000 | millimeter (mm) | convert → |
| 236,220 | pica (pc) | |
| 100,000 | centimeter (cm) | convert → |
| 39,370.1 | inch (in) | convert → |
| 10,000 | decimeter (dm) | |
| 9,842.52 | hand (hh) | |
| 4,970.97 | link (li) | |
| 3,280.84 | foot (ft) | convert → |
| 3,280.83 | US survey foot (ftUS) | |
| 1,093.61 | yard (yd) | convert → |
| 1,000 | meter (m) | convert → |
| 546.807 | fathom (ftm) | |
| 198.839 | rod (rd) | |
| 49.7097 | chain (ch) | |
| 5.39957 | cable length (cb) | |
| 4.97097 | furlong (fur) | |
| 1 | kilometer (km)this unit | |
| 0.621371 | mile (mi) | convert → |
| 0.539957 | nautical mile (nmi) | |
| 0.207124 | league (lea) | |
| 0.001 | megameter (Mm) | |
| 0.000156961 | Earth radius (REarth) | |
| 0.00000333564 | light-second (ls) | |
| 0.00000260146 | lunar distance (LD) | |
| 0.0000014374 | solar radius (Rsun) | |
| 5.55940e-08 | light-minute (lmin) | |
| 6.68459e-09 | astronomical unit (AU) | |
| 1.05700e-13 | light-year (ly) | |
| 3.24078e-14 | parsec (pc) | |
| 3.24078e-17 | kiloparsec (kpc) | |
| 3.24078e-20 | megaparsec (Mpc) | |
| 3.24078e-23 | gigaparsec (Gpc) |