Light Travel Time Calculator
Find the light travel time across any distance.
Result
How to use
- Enter your values in the fields above.
- Press Calculate to see your result instantly.
- Use the Share button to copy a link to your result.
About this calculator
This calculator finds how long light takes to travel a given distance, using time = distance / c, where c is the speed of light (about 299,792 km/s, or exactly 1 light-year per year by definition). It accepts distances in kilometers, astronomical units (AU, the Earth-Sun distance), or light-years, making it easy to work across scales from planetary to interstellar.
Astronomers and students use it to translate huge cosmic distances into something intuitive: sunlight takes about 8 minutes to reach Earth, light from the Moon takes about 1.3 seconds, and light from the nearest star beyond the Sun (Proxima Centauri) takes about 4.2 years — meaning we always see space as it looked in the past. Enter a distance and unit to get the travel time in seconds, minutes, hours, or years as appropriate.
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