how many au's in a light year
1 light-year = 63240 AU (astronomical units) Just for information, 1 light-year is equivalent to the distance travelled by light in 1 year moving in a vacuum. 1 light-year is about 9.4607 * 1015 metres. 1 astronomical unit (AU) is equivalent to the average radius of the Earth's orbit. 1 AU is about 1.4960 * 1011 metres. Simple arithmetic calculation yields the answer that 1 light-year = 63240 AU to a good approximation.