NukeSimulation.com
Named weapon
Little Boy blast radius (15 kt)
Last updated
Little Boy is this globe’s 15 kt airburst preset — the round yield used for Hiroshima. It is also the default on every modern-city page so those cities can be compared on one scale.
Open Little Boy 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.
| 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 |
The real Little Boy was a uranium gun-type bomb. This simulator does not model gun-type internals, only yield and burst height. Optimum airburst here is chosen to maximise 5 psi on the ground in the scaling, not to match a surveyed 1945 altitude.
Fifteen kilotons is small next to thermonuclear weapons and large next to a city block. That is why the city index uses it. If every capital were shown with Tsar Bomba, you would learn nothing about ordinary strategic scales either.
Named weapons, including this one, stay on the free globe. Open Hiroshima for the historic pin, or New York and London for the same rings on cities people recognise.
See this yield on a place
Hiroshima · New York · London · Tokyo
Other weapons
Little Boy · Fat Man · W76-2 · W76-1 · W87 · W88 · B83 · B53 · Ivy Mike · Castle Bravo · B41 · Tsar Bomba
Open the simulator · How the numbers work · FAQ · Privacy · Terms · support@nukesimulation.com