How to Use the Space Distance Unit Converter
Distances within the solar system are usually measured in astronomical units (AU) โ about 149.6 million km, the average Earth-Sun distance. But distances between stars are so much larger that astronomers switch to light-years (the distance light travels in one year) or parsecs (based on a parallax angle of one arcsecond). These units are hard to compare intuitively because the numbers are so vast.
Enter a value, select its original unit (km, AU, ly, or pc), and instantly see it converted into the other three units in a table. For reference, 1 AU โ 149.6 million km, 1 light-year โ 9.46 trillion km (about 63,241 AU), and 1 parsec โ 3.26 light-years.
Use this tool to convert the distance to the nearest star, Proxima Centauri (about 4.24 light-years), into kilometers, translate parsec figures from astronomy papers or documentaries into more intuitive numbers, or build science lesson content involving space distances.
Frequently Asked Questions
A light-year is the distance light travels in a vacuum in one year โ about 9.4607 trillion km (9.4607ร10ยนยฒ km), or roughly 63,241 astronomical units (AU).
A parsec (pc) is defined as the distance at which the radius of Earth's orbit (1 AU) subtends an angle of one arcsecond. It equals about 3.26 light-years, or roughly 30.857 trillion km, and is commonly used in astronomy papers to express distances between galaxies.