How to convert kilometers to astronomical units
au = km × 6.684587122×10⁻⁹Multiply the value in kilometers by 6.684587122×10⁻⁹. To go the other way, multiply by 149,597,870.7 (or divide by 6.684587122×10⁻⁹).
A kilometer is smaller than an astronomical unit: it takes 149,597,870.7 kilometers to make one astronomical unit.
Worked examples
- 1 kilometer1 km × 6.684587122×10⁻⁹ = 6.684587122×10⁻⁹ au
- 5 kilometers5 km × 6.684587122×10⁻⁹ = 3.342293561×10⁻⁸ au
- 10 kilometers10 km × 6.684587122×10⁻⁹ = 6.684587122×10⁻⁸ au
- 20 kilometers20 km × 6.684587122×10⁻⁹ = 1.336917424×10⁻⁷ au
- 100 kilometers100 km × 6.684587122×10⁻⁹ = 6.684587122×10⁻⁷ au
Kilometers to astronomical units conversion table
Values are calculated by the conversion engine and rounded to 8 significant figures.
| Kilometers (km) | Astronomical units (au) |
|---|---|
| 0.1 km | 6.6845871×10⁻¹⁰ au |
| 0.25 km | 1.6711468×10⁻⁹ au |
| 0.5 km | 3.3422936×10⁻⁹ au |
| 1 km | 6.6845871×10⁻⁹ au |
| 2 km | 1.3369174×10⁻⁸ au |
| 3 km | 2.0053761×10⁻⁸ au |
| 4 km | 2.6738348×10⁻⁸ au |
| 5 km | 3.3422936×10⁻⁸ au |
| 6 km | 4.0107523×10⁻⁸ au |
| 7 km | 4.679211×10⁻⁸ au |
| 8 km | 5.3476697×10⁻⁸ au |
| 9 km | 6.0161284×10⁻⁸ au |
| 10 km | 6.6845871×10⁻⁸ au |
| Kilometers (km) | Astronomical units (au) |
|---|---|
| 12 km | 8.0215045×10⁻⁸ au |
| 15 km | 1.0026881×10⁻⁷ au |
| 20 km | 1.3369174×10⁻⁷ au |
| 25 km | 1.6711468×10⁻⁷ au |
| 30 km | 2.0053761×10⁻⁷ au |
| 40 km | 2.6738348×10⁻⁷ au |
| 50 km | 3.3422936×10⁻⁷ au |
| 75 km | 5.0134403×10⁻⁷ au |
| 100 km | 6.6845871×10⁻⁷ au |
| 250 km | 0.0000016711468 au |
| 500 km | 0.0000033422936 au |
| 1,000 km | 0.0000066845871 au |
About the units
Kilometer (km)
One thousand metres. Kilometres measure road distances and running races in most countries; a 10K race is 10 km, about 6.2 miles. One kilometer equals 1,000 meters (m).
Astronomical unit (au)
Exactly 149,597,870,700 m (IAU 2012), roughly the average Earth–Sun distance.
Frequently asked questions
How many astronomical units are in one kilometer?
There are 6.684587122×10⁻⁹ astronomical units in one kilometer, and this value is exact by definition.
How do I convert kilometers to astronomical units?
Multiply the number of kilometers by 6.684587122×10⁻⁹. For example, 10 km × 6.684587122×10⁻⁹ = 6.684587122×10⁻⁸ au.
How many kilometers are in one astronomical unit?
One astronomical unit equals 149,597,870.7 kilometers. That is the reverse factor, 1 ÷ 6.684587122×10⁻⁹.
What is 10 kilometers in astronomical units?
10 km = 6.684587122×10⁻⁸ au.
Is this km to au converter accurate?
Yes. Both units are defined exactly in terms of SI units, so the conversion factor is exact; results are shown to 12 significant figures by default and you can change precision in the converter. Calculations run in your browser using the same tested engine that generated this page.