Kaboomly / Hiroshima blast radius
Hiroshima Bomb Blast Radius
There is no single Hiroshima blast radius. In this simplified model, a Little Boy-size airburst has a 5 psi overpressure radius of 1.6 km (0.98 mi), while the 1 psi ring reaches 4.5 km (2.8 mi).
The bombing of Hiroshima was a human tragedy. This page explains distances with care; it is not a reenactment or a prediction for any real event.
Little Boy: yield and height
The US National Archives reports an estimated yield of 15 kt. The National Park Service describes a height of about 600 m. The simulator uses a fixed Hiroshima-reference height of 0.54 km (0.34 mi); historical source rounding and the model convention should be distinguished.
Model effects by distance
| Effect threshold | Radius |
|---|---|
| Fireball | 0.16 km (0.10 mi) |
| 20 psi overpressure | 0.42 km (0.26 mi) |
| 5 psi overpressure | 1.6 km (0.98 mi) |
| 1 psi overpressure | 4.5 km (2.8 mi) |
| Thermal threshold used by the simulator | 2.2 km (1.3 mi) |
| 500 rem initial radiation | 1.3 km (0.84 mi) |
Model estimates and historical observations
Hiroshima City describes major damage to wooden buildings even beyond the central area. Such observations combine local building conditions and multiple effects. They are not measurements of a single pressure threshold, so a model ring cannot be treated as an exact boundary of the historical damage.
Why sources give different distances
Sources may describe different pressure thresholds, building types, fire effects, or rounding of the yield and burst height. A radius and a diameter also describe different lengths. Compare definitions before comparing numbers.
Model limitations
The estimates assume simplified conditions. Terrain, shielding, weather and buildings vary, and effects do not stop abruptly at a circle. This is not a civil-defense planning tool.
Frequently asked questions
Was every effect confined to one circle?
No. Each threshold has a different radius, and historical conditions varied across the city.
Are these historical measurements?
No. The table is output from Kaboomly’s model based on Glasstone & Dolan. Historical observations are discussed separately.
Sources
- Glasstone & Dolan, The Effects of Nuclear Weapons (1977) — model basis and project references.
- US National Archives: Little Boy — yield.
- National Park Service: Reflection & Remembrance — historical burst height.
- Hiroshima City: The Realities of the Atomic Bombing — observed building damage.