Light Travel Time Calculator
Calculate how long light takes to travel a given distance, from light-minutes to light-years, for stars and planets, free in your browser.
100% FreeRuns in your browserBasic
Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the distance in kilometres.
- Read the time light takes.
How it works
Time = distance ÷ the speed of light (299,792.458 km/s).
Worked example
Sun to Earth (149.6 million km). ≈ 499 s = 8.3 minutes.
Common mistakes
- Mixing up distance units — enter kilometres.
- Forgetting how vast space is — even light takes years to cross it.
Frequently asked questions
How far is a light-year?
About 9.46 trillion km — the distance light travels in one year.
Related tools
- Focal Ratio Calculator
- Weight on Other Planets Calculator
- Light-Year Converter
- Angular Size Calculator
- Planet Weight Calculator
- Escape Velocity Calculator
Explore more in Astronomy & Navigation.
Cite this tool
Zerdly. (2026). Light Travel Time Calculator. Retrieved from https://www.zerdly.com/tools/light-travel-time-calculator/
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.