# astronomical unit

##### Non-SI unit accepted for use with SI
Name Symbol Quantity Value in SI units
astronomical unit au length 149 597 870 700 m
149.597 870 7 Gm

### Definition

The astronomical unit, symbol au, is a non-SI unit of length accepted for use with the SI.

One astronomical unit is equal to 149 597 870 700 m, or approximately 150 gigametres.

The astronomical unit is approximately equal to the average distance from the Earth to the Sun. It is used primarily in the field of astronomy for measuring distances within the Solar System, or interplanetary distances around other stars.

##### Examples of distances of planets from the Sun
 Name Distance in au Distance in SI units Mercury 0.387 58 Gm Venus 0.723 108 Gm Earth 1 150 Gm Mars 1.52 228 Gm Jupiter 5.20 778 Gm Saturn 9.54 1427 Gm Uranus 19.2 2871 Gm Neptune 30.1 4495 Gm