ToolsDistance to Lightning Strike

Distance to Lightning Strike

Calculate lightning strike distance based on the flash-to-bang time difference.

⚡ Start timer when you see lightning, stop when you hear thunder

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How It Works

Sound travels through air at approximately 1,125 ft/s (343 m/s). Every 5 seconds between lightning flash and thunder represents roughly 1 mile of distance (or ~3 seconds per kilometer).

Distance to Lightning Strike How Is It Calculated?

While light reaches our eyes almost instantly, sound waves travel much more slowly through air. This speed difference makes the time delay between lightning and thunder a useful tool for calculating storm distance.

The speed of sound in air is approximately 343 metres per second (or 1,235 km/h), and this value varies slightly with temperature. The formula is simple: Distance (km) = Elapsed time (s) × 0.343. For example, if 5 seconds pass between lightning and thunder, the storm is approximately 1.7 km away.

Safety rules: According to the NOAA 30-30 lightning rule: if the time between flash and thunder is under 30 seconds (within 6 miles), seek substantial shelter immediately. Remain indoors for at least 30 minutes after the last sound of thunder.

This tool offers both a manual duration input and an interactive stopwatch, calculating distance the moment you hear thunder.