B61 on Tokyo
340 kt thermonuclear weapon · Japan · Population 13,960,000 · Density 6,300/km²
About this scenario
This page calculates what would happen if the B61 (USA, 1968) detonated over Tokyo (Japan). Variable yield tactical bomb.
The capital of Japan and the world's largest metropolitan area; Greater Tokyo holds over 37 million people. With an urban-core density of about 6,300 people per km², even a relatively small detonation over the city center would affect a large population.
The B61 delivers 340 kt of explosive yield — 23× more powerful than the Hiroshima bomb. The tables below show calculated effect radii for an air burst (optimized for blast spread) and a surface burst (which produces massive fallout).
Air-burst effects (B61 over Tokyo)
| Effect zone | Radius | Est. affected |
|---|---|---|
| Fireball (vaporization, 100% fatal) | 1.49 km | ~44,097 |
| Severe blast (20 PSI, ~98% fatal) | 3.30 km | ~167,051 |
| Moderate blast (5 PSI, ~50% fatal) | 7.05 km | ~384,211 |
| Light blast (1 PSI, glass injuries) | 20.06 km | ~348,887 |
| 3rd-degree thermal burns | 7.31 km | — |
| 2nd-degree thermal burns | 13.09 km | — |
Estimated total fatalities: ~595,359 · Estimated total affected (inside 1 PSI light-blast radius): ~7,961,626.
Surface-burst effects (with fallout)
A surface burst trades blast spread for radioactive fallout — much smaller blast radii but a large lethal fallout plume drifting downwind. This is what would happen if the B61 struck ground level rather than detonating optimally above Tokyo.
| Effect zone | Radius (surface burst) |
|---|---|
| Fireball | 1.19 km |
| Severe blast (20 PSI) | 1.81 km |
| Moderate blast (5 PSI) | 3.88 km |
| Light blast (1 PSI) | 11.03 km |
| 3rd-degree thermal burns | 4.39 km |
| Lethal fallout zone | ~123.5 km |
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See the actual blast zones overlaid on a map of Tokyo with population-density-based casualty estimates updated in real time as you move the detonation point.
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Other weapons on Tokyo
FAQ
What would happen if the B61 detonated over Tokyo?
In an air burst over Tokyo, the B61 (340 kt) would produce a fireball about 1.49 km in radius. The 5 PSI moderate-blast zone — where most residential buildings collapse — would extend to 7.05 km. Light blast damage and shattered windows would reach 20.06 km. Given Tokyo's urban density (~6,300/km²), this scenario yields an estimated 595,359 immediate fatalities and about 348,887 additional injured.
How many people would die in Tokyo from a B61 strike?
An air burst of the B61 over Tokyo could cause an estimated 595,359 immediate fatalities and 348,887 additional injuries. The fireball alone (radius 1.49 km) would kill approximately 44,097 people; the severe-blast zone (20 PSI, radius 3.30 km) would add 167,051; the moderate-blast zone (5 PSI, radius 7.05 km) would add 384,211 more. Real numbers depend heavily on time of day, sheltering, weather, and altitude of detonation.
What is the blast radius of the B61 on Tokyo?
For an air burst over Tokyo: fireball 1.49 km, severe blast (20 PSI) 3.30 km, moderate blast (5 PSI) 7.05 km, light blast (1 PSI) 20.06 km. Thermal radiation causes 3rd-degree burns out to 7.31 km. A surface burst would shrink the blast radii by roughly 40 percent but generate massive radioactive fallout extending ~124 km from ground zero.
Is the B61 bigger than the bomb that hit Hiroshima?
The Hiroshima bomb (Little Boy) had a yield of about 15 kilotons. The B61 at 340 kt is 23× more powerful than the Hiroshima bomb.