Frequently Asked Questions
Everything you need to know about the Light-Year Converter.
What is a light-year?
The distance light travels in one Julian year (365.25 days) at 299,792,458 m/s — about 9.46 trillion kilometers.
How does this converter work?
Enter a value in any supported unit (light-years, AU, parsecs, km, miles, etc.) and every other unit updates instantly.
Is it free?
Completely free, no sign-up, downloads, or limits.
What units can I convert between?
Light-years, light-seconds/minutes/hours/days, astronomical units, parsecs, kilometers, and miles.
What's the difference between a light-year and a parsec?
A parsec is about 3.26 light-years; both measure astronomical distance, but parsecs are derived from stellar parallax angles.
Can I find out how long light takes to travel a distance?
Yes, use the light-travel-time mode: enter a distance and get the travel time formatted in years, days, hours, minutes, or seconds.
How accurate are the conversions?
Uses the exact defined speed of light and standard AU/parsec definitions for precise results.
Does it handle very large or small numbers?
Yes, results are shown in both scientific notation and plain decimal.
Is my data stored?
No; everything runs in your browser and isn't stored or sent anywhere.
Does it work on mobile?
Yes, fully responsive on all screen sizes.