Fat Man’s blast radius was about 1 mile (1.6 km) wide for the main blast- damage zone, according to the National Park Service’s summary of the Nagasaki bombing.

Quick context

The bomb detonated above Nagasaki, and the surrounding geography limited destruction compared with Hiroshima. Even so, the explosion still obliterated nearly half the city.

Important nuance

“Blast radius” can mean different things depending on whether you mean:

  • the fireball,
  • severe structural damage,
  • thermal burns, or
  • the broader area of destruction.

Some modern breakdowns estimate wider effect zones, with thermal effects reaching roughly 2.2 km in radius, but the classic blast-damage radius is commonly given as about 1 mile.