# Kilometers to Astronomical Units (km to au)

Source: https://www.unitconvertercalculator.com/length/kilometers-to-astronomical-units/

**1 km = 6.6845871222684E-9 au**

One kilometer equals approximately 6.685 x 10-9 astronomical units, or about 6.7 billionths of an AU. The Earth-Sun distance (1 AU) is about 149,597,871 km. This conversion is essential in solar system science where distances are given in both units.

## Formula

Convert Kilometers to Astronomical Units

## Conversion Table

| Kilometers (km) | Astronomical Units (au) |
|---|---|
| 1 km | 6.68458712226E-9 au |
| 5 km | 3.342293561134E-8 au |
| 10 km | 6.684587122268E-8 au |
| 42.195 km | 2.8205615362411E-7 au |
| 100 km | 6.6845871222684E-7 au |
| 500 km | 3.3422935611342E-6 au |
| 1000 km | 6.6845871222684E-6 au |
| 10000 km | 6.6845871222684E-5 au |
| 100000 km | 0.00066845871222684 au |
| 1000000 km | 0.0066845871222684 au |
| 10000000 km | 0.066845871222684 au |
| 149597871 km | 1.0000000020054 au |

## Units

### Kilometer (km)

A metric unit of length equal to 1000 meters. The standard unit for measuring road distances and geographic distances in most countries.

### Astronomical Unit (au)

Exactly 149,597,870,700 meters by IAU 2012 definition. Roughly the average distance from the Earth to the Sun. Used for distances within our solar system.

## Background

The Earth-Sun distance (1 AU) is 149,597,871 km. Mars at closest approach is about 54.6 million km (0.365 AU). Jupiter is about 628 million km (4.2 AU). When space agencies report mission distances in kilometers, astronomers convert to AU for solar system context.

## Good to Know

NASA reports spacecraft positions in kilometers. Astronomers discuss planetary positions in AU. The Mars rover team says '225 million km from Earth.' An astronomer says '1.5 AU.' Same distance, different audience, different unit.

## FAQ

### How many AU is 1 kilometer?

One kilometer equals approximately 6.685 x 10-9 AU. One AU is about 149.6 million km.

### How many kilometers are in 1 AU?

One AU contains approximately 149,597,871 km (about 149.6 million km).

### When is this conversion used?

In space science. Mission distances are reported in km by space agencies, but astronomers prefer AU for solar system scale. Both units coexist in planetary science.

## Non-Frequently Asked Questions

### How many km is a road trip to Mars?

Mars is between 55 and 400 million km from Earth depending on orbital position. At closest approach, it is about 0.37 AU. Your GPS would need a serious software update.

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## See Also

- [Astronomical Units to Kilometers](https://www.unitconvertercalculator.com/length/astronomical-units-to-kilometers/)