How It Works

Can you calculate how far away lightning struck?

Lightning over Romania

We can calculate how far something travelled if we know its
speed and the time it has been travelling using this equation:
Distance = Speed x Time. The speed of light is very fast, at roughly
300,000,000 metres per second, so we see lightning almost
instantaneously. In comparison, sound travels through air at
around 330–350 metres per second, depending on temperature
and humidity. You can work out how far away the lightning struck
by measuring the time between seeing the lightning and hearing
the thunder, then multiplying by the speed of sound. For example,
if you count ten seconds before hearing the thunder, the lightning
struck roughly 3,300 metres away.

  • Randy

    I use the method my dad taught me and the numbers are smaller. Count the number of seconds between flash and the start of thunder divide the number of seconds by 5. the result is th approximate distance in miles. Maybe Im just a math dummy