Astronomical Unit (AU) - Unit Information & Conversion
What is a Astronomical Unit?
Definition
An astronomical unit is a unit of length roughly equal to the average distance between Earth and the Sun. It is defined as exactly 149,597,870,700 meters.
History
Historically used to measure distances within the Solar System, its value was refined over centuries through astronomical observations. The exact definition was adopted by the IAU in 2012.
Common Uses
- Measuring distances within the Solar System (e.g., planet orbits)
- Expressing distances to near-Earth objects
Unit FAQs
Why use Astronomical Units instead of kilometers or miles?
Astronomical Units (AU) provide a more convenient scale for the vast distances within our solar system. Expressing interplanetary distances in km or miles results in extremely large and unwieldy numbers.
How many kilometers/miles is 1 AU?
1 Astronomical Unit (AU) is approximately 149.6 million kilometers or 93 million miles.
How long does it take light to travel 1 AU?
It takes sunlight approximately 8 minutes and 20 seconds to travel the distance of one Astronomical Unit from the Sun to the Earth.
Astronomical Unit Conversion Formulas
To Meter:
To Kilometer:
To Centimeter:
To Millimeter:
To Inch:
To Foot:
To Yard:
To Mile:
To Nautical Mile:
To Micrometer:
To Nanometer:
To Light Year:
To Point (Typography):
To Mil/Thou:
Convert Astronomical Unit
Need to convert Astronomical Unit to other length units? Use our conversion tool.