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Calcimator

Lightning Distance Calculator

Calculate the distance to a lightning strike from the flash-to-bang time delay. Includes temperature-adjusted speed of sound and safety guidance.

Inputs

seconds
°F

Results

Distance

3.46 km

≈ 10 Eiffel Towers

Safety Assessment

Danger — Move indoors, lightning within striking range

Distance2.15 miles
Distance3,460 m
Rule of Thumb (t/2.94)3.4 km
Speed of Sound346.5 m/s
Storm Arrival (at 40 km/h)5.2 min
How to Use This Calculator
  1. Count the seconds between the lightning flash and the thunder clap and enter as Flash-to-Bang Time (seconds).
  2. Optionally enter Air Temperature (°C) to refine the speed of sound calculation.
  3. Review Distance (km) and Distance (miles) to the lightning strike.
  4. Check Safety Assessment: under 10 km (6 miles) = seek shelter immediately.
  5. Monitor Storm Arrival (at 40 km/h) to estimate how quickly the storm is approaching your location.

How the result changes with Flash-to-Bang Time

Flash-to-Bang TimeDistanceSafety Assessment
6.452.23 kmVery Dangerous — Lightning is very close
217.28 kmDanger — Move indoors, lightning within striking range
3913.51 kmCaution — Storm approaching, prepare to take shelter
5418.71 kmSafe

What each input means

Flash-to-Bang Time
Count the seconds between seeing the lightning flash and hearing the thunder. Start counting at the flash.
Air Temperature
Current air temperature in °C. Sound travels faster in warmer air, affecting the distance calculation.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    Flash-to-Bang Time = 10, Air Temperature = 25 = 2 input(s) provided
  2. Calculate Distance
    Distance = speedOfSoundKmPerS
    3.46 = 3.46
  3. Calculate Safety Assessment
    Safety Assessment
    Danger — Move indoors, lightning within striking range = Danger — Move indoors, lightning within striking range
  4. Calculate Distance
    Distance
    2.15 = 2.15
  5. Calculate Distance
    Distance
    3460 = 3460

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