Estimate how far away lightning is by timing the seconds between seeing the flash and hearing thunder. This calculator converts the delay into miles, kilometers, feet, meters, and gives simple storm distance guidance.
Time delay:
Enter the number of seconds between seeing the lightning flash and hearing thunder.
Simple rule:
The calculator estimates distance by using about 5 seconds per mile, or about 3 seconds per kilometer.
Temperature adjusted method:
Sound speed changes slightly with air temperature, so this option uses the entered temperature to refine the estimate.
Distance result:
The result shows how far away the lightning is in miles, kilometers, feet, and meters.
A lightning distance calculator is useful for storm tracking, outdoor activities, sports events, camping, hiking, boating, yard work, and deciding when to move indoors during thunderstorms.
This calculator gives an estimate only. Lightning can strike miles from the main storm, so always follow official weather alerts and local safety rules.
Your result estimates the distance to the lightning strike based on how long sound took to reach you. A shorter delay means the lightning is closer. A longer delay means it is farther away.
Count the seconds between lightning and thunder, then divide by about 5 to estimate miles away.
Using the simple rule, 5 seconds is about 1 mile away.
Using the simple rule, 30 seconds is about 6 miles away.
Light travels much faster than sound, so the flash reaches your eyes before the thunder reaches your ears.