Light-Time Calculator
Calculate how long light or a radio signal takes to travel a given astronomical distance.
Result
How it works
Calculate how long light or a radio signal takes to travel a given astronomical distance.
How to use this calculator
What to enter
Enter or select the following as requested: Distance (million km). Follow the units, valid ranges, examples, and options displayed beside each field.
What the result means
The astronomy result converts or estimates a distance, time, brightness, gravity, or orbital quantity from the entered astronomical values and model. Check the units, reference frame, object assumptions, and whether the formula uses idealized orbital or observational conditions.
When to use it
Use this for astronomy learning or preliminary calculations. Confirm the units and scientific model and consult reliable observational data when precision matters.