---
title: "Kilometers to Astronomical units — km to AU converter"
description: "1 kilometer = 6.685 × 10^-9 astronomical units. Conversion table, the exact formula, and a calculator for any value."
url: https://atoneplace.net/convert/km-to-astronomical-units/
site: "At One Place"
---

# Kilometers to astronomical units

**1 kilometer in astronomical units: 1 km = 6.685 × 10^-9 AU**

AU = km × 6.684587122 × 10^-9

To convert kilometers to astronomical units, multiply by 6.684587122 × 10^-9. The table below gives the values people look up most often, and the converter works for any number.

## Kilometers to astronomical units table

*Common kilometer values converted to astronomical units.*

| Kilometers | Astronomical units |
| --- | --- |
| 1 km | 6.685 × 10^-9 |
| 2 km | 1.337 × 10^-8 |
| 3 km | 2.005 × 10^-8 |
| 4 km | 2.674 × 10^-8 |
| 5 km | 3.342 × 10^-8 |
| 10 km | 6.685 × 10^-8 |
| 15 km | 1.003 × 10^-7 |
| 20 km | 1.337 × 10^-7 |
| 25 km | 1.671 × 10^-7 |
| 30 km | 2.005 × 10^-7 |
| 40 km | 2.674 × 10^-7 |
| 50 km | 3.342 × 10^-7 |
| 75 km | 5.013 × 10^-7 |
| 100 km | 6.685 × 10^-7 |
| 250 km | 0.000001671 |
| 500 km | 0.000003342 |
| 1,000 km | 0.000006685 |

## How the conversion works

The relationship is AU = km × 6.684587122 × 10^-9. Both units measure length, so the conversion is a fixed factor that never changes.

## Common questions

### How many astronomical units are in one kilometer?

One kilometer equals 6.685 × 10^-9 astronomical units. AU = km × 6.684587122 × 10^-9.

### How do you convert kilometers to astronomical units?

Use AU = km × 6.684587122 × 10^-9. So 10 km is 6.685 × 10^-8 AU.

### How many kilometers are in one astronomical unit?

One astronomical unit equals 149,597,870 kilometers, which is the reverse of the conversion above.

## Related pages

- [Astronomical units to Kilometers](https://atoneplace.net/convert/astronomical-units-to-km/)
- [Kilometers to Meters](https://atoneplace.net/convert/km-to-meters/)
- [Kilometers to Centimeters](https://atoneplace.net/convert/km-to-cm/)
- [Kilometers to Millimeters](https://atoneplace.net/convert/km-to-mm/)
- [Kilometers to Miles](https://atoneplace.net/convert/km-to-miles/)
- [Kilometers to Yards](https://atoneplace.net/convert/km-to-yards/)
- [Kilometers to Feet](https://atoneplace.net/convert/km-to-feet/)
- [Kilometers to Inches](https://atoneplace.net/convert/km-to-inches/)

## Sources

- Guide for the Use of the International System of Units (SP 811) — NIST (https://www.nist.gov/pml/special-publication-811) [Public domain (US Government)]
- The International System of Units (SI Brochure) — Bureau International des Poids et Mesures (https://www.bipm.org/en/publications/si-brochure)
- Calculated on this page — At One Place (/about/)