Light Travel Time Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
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
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.