A light-year is a unit of distance that represents how far light travels in one year. Light moves at a speed of about 186,000 miles per second (300,000 kilometers per second) in a vacuum. Over the course of one year, this adds up to approximately 5.88 trillion miles or about 9.46 trillion kilometers

. To put it precisely, the International Astronomical Union defines a light- year as the distance light travels in one Julian year (365.25 days), which equals exactly 9,460,730,472,580.8 meters (about 9.46 trillion kilometers)

. In summary:

• 1 light-year ≈ 5.88 trillion miles (9.46 trillion kilometers)
• It is a measure of distance, not time
• Used primarily to express astronomical distances between stars and galaxies