Convert length and distance units — meters, feet, inches, kilometers, miles, light years and more.
| Unit | Name | Value |
|---|---|---|
| 0.001 km | 6.684e-12 au | |
| 0.01 km | 6.684e-11 au | |
| 0.1 km | 6.684e-10 au | |
| 1 km | 6.68449e-09 au | |
| 5 km | 3.34225e-08 au | |
| 10 km | 6.68449e-08 au | |
| 50 km | 3.34225e-07 au | |
| 100 km | 6.68449e-07 au | |
| 1000 km | 6.68449e-06 au |
Multiply the number of Kilometers by 6.6845×10-9 to get Astronomical Units. Formula: au = km × 6.6845×10-9. Example: 10 km × 6.6845×10-9 = 6.6845×10-8 au. To reverse, divide Astronomical Units by 6.6845×10-9 to get Kilometers.
| Kilometer (km) | Astronomical Unit (au) |
|---|---|
| 0.001 km | 6.6845×10-12 au |
| 0.01 km | 6.6845×10-11 au |
| 0.1 km | 6.6845×10-10 au |
| 0.5 km | 3.3422×10-9 au |
| 1 km | 6.6845×10-9 au |
| 2 km | 1.3369×10-8 au |
| 5 km | 3.3422×10-8 au |
| 10 km | 6.6845×10-8 au |
| 20 km | 1.3369e-07 au |
| 50 km | 3.34225e-07 au |
| 100 km | 6.68449e-07 au |
| 250 km | 1.67112e-06 au |
| 500 km | 3.34225e-06 au |
| 1000 km | 6.68449e-06 au |
| 10000 km | 6.68449e-05 au |
To convert Kilometer to Astronomical Unit, multiply by 6.6845×10-9. Example: 10 km = 6.6845×10-8 au
To convert Astronomical Unit back to Kilometer, divide by 6.6845×10-9 (multiply by 149600000). Use the swap button above.
Start with 100 Kilometers = 6.68449e-07 au as your reference point. Scale up or down from there.
Mission planners express spacecraft distances in AU for scientific context but convert to kilometres for precise navigation commands, thruster burn timing, and deep-space communication delay calculations.
Asteroid and comet tracking reports distance in both AU (for orbital context) and kilometres (for close-approach distance). Planetary defence researchers convert between the two for impact probability calculations.
Solar wind propagation is modelled in AU while particle interaction physics uses kilometres. Space plasma physicists convert between the two when correlating solar observations with in-situ spacecraft measurements.
Signal travel times between Earth and spacecraft are calculated using kilometre-based light-speed equations, then expressed in AU for mission reports. Engineers convert between km and AU in every deep-space communication design.
Astronomy teachers convert AU distances to kilometres to make planetary distances tangible — "Mars is 0.52–2.52 AU away, or 78–378 million kilometres" bridges abstract orbital parameters with familiar distance units.
Comet perihelion distances are expressed in AU while coma size (the gas cloud around the nucleus) is measured in kilometres — cometary scientists convert between AU and km in every apparition analysis.
The Kilometer is a unit of Length measurement (symbol: km). 1 km = 6.6845×10-9 au. Used in scientific and practical Length measurement applications.
The Astronomical Unit is a unit of Length measurement (symbol: au). It is part of an internationally recognised measurement system used alongside the Kilometer.
The kilometre was introduced in 1795 as part of the French metric system — exactly 1,000 metres. France was the first country to adopt a universal decimal measurement system, replacing a chaotic patchwork of regional units. The metre itself was defined as one ten-millionth of the distance from the North Pole to the equator through Paris. By the 20th century, the kilometre had become the world's standard unit for road distances, replacing miles in country after country. The US remains the only major exception, still officially using miles for road distances.
The astronomical unit has ancient roots — Aristarchus of Samos attempted to measure the Earth-Sun distance around 270 BC. For centuries the AU was estimated using Venus transit observations. Edmond Halley organised the first coordinated international transit-of-Venus expedition in 1716. The modern value was determined by radar ranging to Venus in 1961. The IAU formally defined the AU as exactly 149,597,870,700 metres in 2012 — a fixed constant of physics, not a measured distance.
Common use: Kilometer to Astronomical Unit conversion is needed when working with international standards, scientific publications, or reference materials that use different unit systems for Length measurement.