How many kilometres is one astronomical unit?

One astronomical unit is exactly 149,597,870.7 kilometres, which is the average distance between the Earth and the Sun.

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Astronomical

Astronomical Unit Calculator

Convert astronomical units (AU) — the average Earth–Sun distance — to kilometres, miles, light years, and metres, with a full equivalents table.

Result

149,597,871 km

Equivalent distance

Your value in astronomical units, gigametres, and kilometres.

How it works

The astronomical unit is a convenient yardstick for the Solar System, defined as exactly 149,597,870.7 km. Larger interstellar distances use light years or parsecs. All relate to the metre, so conversion is a matter of scaling.

1 AU = 149,597,870.7 km
1 light year ≈ 63,241 AU · 1 parsec ≈ 206,265 AU

Worked example

Neptune orbits at about 30 AU, which is 30 × 149,597,871 ≈ 4.49 billion km from the Sun.

Frequently asked questions

How many kilometres is one AU?

149,597,870.7 km — the mean Earth–Sun distance.

How many AU are in a light year?

About 63,241 AU.