Light Year Calculator

What Is a Light-Year?

A light-year is the distance light travels in one Julian year (365.25 days) through a vacuum, equal to about 9.4607 × 10¹² kilometers (roughly 5.879 trillion miles). It’s a unit of distance, not time, despite the name — astronomers use it because interstellar distances in kilometers or miles would involve unwieldy numbers.

This calculator converts any distance in light-years into kilometers, miles, and astronomical units (AU, the Earth-Sun distance, about 150 million km), using the standard conversion 1 light-year = 63,241.1 AU.