Convert Astronomical Units Online - Free AU to km, miles, light years Converter

What is the Astronomical Unit Converter?

The Astronomical Unit Converter is a free online tool that converts astronomical units (AU) to kilometers, miles, light years, parsecs, and solar radii. Whether you are studying astronomy, planning space missions, or simply curious about the scale of our Solar System, this converter provides accurate real-time conversions. For more length conversions, try our Length Converter and Unit Converter.

What is an Astronomical Unit?

An astronomical unit (symbol: au or AU) is a unit of length approximately equal to the average distance between Earth and the Sun. The International Astronomical Union (IAU) defines it as exactly 149,597,870,700 meters (about 150 million kilometers or 93 million miles). It is the standard unit for measuring distances within our Solar System.

Conversion Values

1 AU = 149,597,870.7 km
1 AU = 92,955,807 miles
1 AU = 0.000015813 light years
1 AU = 4.848 x 10^{-6} parsecs
1 AU = 215.03 solar radii

Planetary Distances in AU

Mercury: 0.39 AU
Venus: 0.72 AU
Earth: 1.00 AU
Mars: 1.52 AU
Jupiter: 5.20 AU
Saturn: 9.58 AU
Uranus: 19.22 AU
Neptune: 30.05 AU
Pluto (dwarf): 39.48 AU

How to Use This Converter

Enter a value in astronomical units (AU).
Select a target unit from the dropdown to see the primary conversion.
View all conversions in the details section, including light travel time.
Use quick examples for planetary distances from Mercury to Neptune.

Frequently Asked Questions

How many kilometers is 1 AU?

One astronomical unit is exactly 149,597,870.7 kilometers. This is the officially defined value adopted by the International Astronomical Union in 2012.

What is the difference between AU and light year?

An AU measures distances within the Solar System (1 AU = Earth-Sun distance), while a light year measures interstellar distances (the distance light travels in one year). One light year equals approximately 63,241 AU. Light years are used for stars and galaxies, while AU is used for planetary distances.

How long does it take light to travel 1 AU?

Light takes approximately 8 minutes and 20 seconds to travel from the Sun to Earth, a distance of 1 AU. This means when you see the Sun, you are actually seeing it as it was about 8 minutes ago.

What is a parsec and how does it relate to AU?

A parsec (pc) is approximately 206,265 AU. It is defined as the distance at which one astronomical unit subtends an angle of one arcsecond. Parsecs are commonly used in professional astronomy for measuring distances to stars and galaxies.

Why was the astronomical unit defined exactly in 2012?

Before 2012, the AU was based on Earth's elliptical orbit, making it slightly variable. The IAU fixed it to exactly 149,597,870,700 meters to provide a stable reference for celestial mechanics, spacecraft navigation, and astronomical calculations.

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Astronomical Unit Converter