Lightning Distance Calculator

Use the Flash-to-Bang method to calculate exactly how far away a storm is.

Time the Delay

0.00 s

Manual Override 5.00 s

Already counted the seconds in your head? Use the slider above to bypass the stopwatch.

1.07 Miles Away

1.72 Kilometers Away

The Physics of a Thunderstorm

The "Flash-to-Bang" method works because of the massive difference between the speed of light and the speed of sound.

The Flash: Light travels at a blistering 186,000 miles per second. For any storm on Earth, the light reaches your eyes almost instantaneously.
The Bang: Sound travels through the air at a much slower 767 miles per hour (about 343 meters per second).
The Math: Because of this speed limit, it takes the sound of thunder exactly 4.69 seconds to travel one mile. The common "Rule of Thumb" is to count the seconds and divide by 5 for miles, or divide by 3 for kilometers. This calculator uses the exact mathematical speed of sound for precise tracking!