# ››Convert light year to astronomical unit

 light years AU

How many light years in 1 AU? The answer is 1.58125074089E-5.
We assume you are converting between light year and astronomical unit.
You can view more details on each measurement unit:
light years or AU
The SI base unit for length is the metre.
1 metre is equal to 1.05700083402E-16 light years, or 6.68458712267E-12 AU.
Note that rounding errors may occur, so always check the results.
Use this page to learn how to convert between light years and astronomical units.
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# ››Definition: Light-year

A light year, abbreviated ly, is the distance light travels in one year: roughly 9.46 × 1012 kilometres (9.46 petametres, or about 5.88 × 1012 (nearly six trillion) miles). More specifically, a light year is defined as the distance that a photon would travel, in free space and infinitely far away from any gravitational or magnetic fields, in one Julian year (365.25 days of 86400 seconds each).

# ››Definition: Astronomical unit

The astronomical unit (AU or au or a.u. or sometimes ua) is a unit of length. It is approximately equal to the mean distance between the Earth and Sun. The currently accepted value of the AU is 149 597 870 691 ± 30 metres (about 150 million kilometres or 93 million miles).

The symbol "ua" is recommended by the Bureau International des Poids et Mesures, but in the United States and other anglophone countries the reverse usage is more common. The International Astronomical Union recommends "au" and international standard ISO 31-1 uses "AU".

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