Light Travel Time Calculator
How long light takes to cross a distance.
Enter your values
Enter the distance you are working with.
Choose one of: Kilometres, Astronomical units, Light years, Parsecs.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Travel time
- 8.32 minutes
- Distance in km
- 1.4960e+8
- In light years
- 1.5812e-5
- In AU
- 1
Quick answer
Light travels 299,792 kilometres every second in a vacuum.
Time = distance ÷ c
At a glance
| What it does | How long light takes to cross a distance. |
|---|---|
| Category | Science |
| Inputs needed | Distance, Unit |
| Main output | Travel time |
| Formula | Time = distance ÷ c |
| Cost | Free — no sign-up, no download |
How to use the Light Travel Time Calculator
- 1Enter the distance value.
- 2Choose the distance unit.
- 3Read light travel time and conversions.
Inputs explained
- Distance
- Enter the distance you are working with.
- Unit
- Choose one of: Kilometres, Astronomical units, Light years, Parsecs.
Worked example
Using the values the calculator loads with:
Inputs
- Distance1
- UnitAstronomical units
Results
- Travel time8.32 minutes
- Distance in km1.4960e+8
- In light years1.5812e-5
- In AU1
Frequently asked questions
How far is one light year?
About 9.46 trillion kilometres.
How long is light from the Sun?
8 minutes 20 seconds.
What do I need to enter into the Light Travel Time Calculator?
Just 2 values: distance, unit. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Light Travel Time Calculator work out the answer?
Light travels 299,792 kilometres every second in a vacuum. It applies the formula Time = distance ÷ c and shows the working so you can check each step by hand.
Is the Light Travel Time Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.