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Lightning Distance from Thunder Delay — result sheet
Estimate how far away a lightning flash was from the time between seeing the flash and hearing thunder.
Inputs used
Results
Visual chart
Breakdown
Calculation steps
Returned data table
Formula and methodology
Formula: distance = sound speed × delay; light-travel time is treated as negligible, and the result is also compared with the NWS five-seconds-per-mile rule of thumb.
Light from a flash reaches an observer far sooner than its thunder. Multiplying the measured delay by the chosen sound speed gives a transparent first estimate in metres, kilometres, and miles. The default speed is a near-sea-level reference; temperature, humidity, wind, terrain, and the length of the lightning channel can change what a listener hears.
This result follows the calculator's declared inputs, precision, validation boundaries, and model limits.
Input contract
- Flash-to-thunder delay — s; minimum 0; maximum 3600
- Speed of sound in air — m/s; minimum 250; maximum 450
Worked example
| Input | Value |
|---|---|
| Flash-to-thunder delay | 15 |
| Speed of sound in air | 343 |
About 5.145 km or 3.198 miles; the five-second rule gives about 3 miles.
Assumptions and limits
- The flash and the loudest heard thunder are treated as coming from the same part of the lightning channel.
- The entered speed of sound is constant along the path and the light-travel time is negligible at this scale.
- Hearing thunder means the storm may be close enough to be dangerous; the calculation is not a safety clearance.
Calculator note
Source and methodology
Use the official WorldCalculate methodology policy for the source, formula, precision, and boundary standards behind this calculator.
Planning estimate, not financial, medical, legal, or professional advice. © WorldCalculate — reuse with attribution. Built and curated by Hassan ALRowaie.
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