Lightning Distance Calculator
Reviewed by Hamza Gujjar, Algorithm Architect & Software Developer
Last updated: July 28, 2026Lightning Distance Calculator
How far away was that lightning strike? This calculator applies the classic flash-to-bang counting method.
Distance (miles) = Seconds Between Flash and Thunder / 5
Example
10 seconds between seeing the flash and hearing thunder:
Distance = 10/5 = ~2.0 miles (3.3 km) away
Why This Method Actually Works
This "flash-to-bang" method works because light travels essentially instantaneously over these distances, while sound travels at roughly 1 mile per 5 seconds (343 m/s) - counting the gap between seeing the flash and hearing the resulting thunder gives a reasonably accurate distance estimate to the strike.
A Useful Safety Rule of Thumb
A commonly cited safety guideline is that if the gap is 30 seconds or less (roughly 6 miles), the storm is close enough to pose a lightning risk, and it's time to seek shelter - lightning can strike well outside the area of visible rainfall, so this counting method remains a useful real-time safety check.