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Tokyo nuclear blast radius

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Tokyo is the world’s largest metro, but this scenario is a 15 kt airburst over Tokyo Station, not a city-killing strike. The rings show how a Hiroshima-scale yield sits on a rail and office core.

Open Tokyo in the 3D simulator

Educational estimate only. Blast and heat rings use simplified yield scaling. They ignore terrain, weather, shielding, and weapon design. Casualty counts use WorldPop 2020 residents on an approximately 1 km grid and ignore time of day, commuting, shelter, and evacuation. This is not a targeting or civil-defense tool. About the model.

Aim point: Tokyo Station / Marunouchi · Weapon: Little Boy (15 kt, 543 m (1,780 ft) optimum airburst)

Ground ranges for Little Boy (15 kt, 543 m (1,780 ft) optimum airburst) in this simulator.
Effect Ground range What the model means
Fireball 266 m (872 ft) Maximum luminous radius
20 psi 839 m (2,751 ft) Heavy destruction
5 psi 1.8 km (1.1 mi) Most buildings collapse
Thermal 2.0 km (1.3 mi) 3rd-degree burns
1 psi 4.2 km (2.6 mi) Windows shatter
Rings scaled to 1 psi. Yellow fireball, red 20 psi, orange 5 psi, gold thermal, blue 1 psi. Not a map of buildings.

Casualty estimate at this pin

People on the WorldPop 2020 grid inside this scenario’s 1 psi ring. Rounded educational estimate, not a forecast.
Estimated deaths 63,821
Estimated injuries 192,246
Residents inside 1 psi 708,098

What the rings cover

The inner rings sit on the station, Marunouchi, and the edge of Ginza. 5 psi stays inside the central wards. 1 psi reaches across a slice of Chiyoda and Chuo and still leaves most of the 23 wards and the greater metro outside the model’s window-breakage radius.

The preset aims at Tokyo Station and the Marunouchi office district, west of the Imperial Palace moat. That is a job-center grid, not a residential ward average, which is why the casualty estimate can look high for a ‘small’ yield.

Tokyo’s wards spread tens of kilometres. Even the 1 psi ring in this model is a neighbourhood-scale disk on that map. The globe is useful here because 2D blast circles hide how the palace, the station, and the Nihonbashi grid sit next to each other in height and street width.

Hiroshima is a short jump from this page if you want the same yield on the city where Little Boy was actually used. Tokyo is the comparison case: a much larger, denser, contemporary core.

Related pages

Seoul · Shanghai · Hiroshima · New York

All cities and sites

City index · Historic sites · Weapon yields

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