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 |
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DefinitionThe 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. |
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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 |
Metric System 