Grand Slam
UK · 1945 · 9.5 tons TNT · conventional high-explosive
Overview
Largest conventional WWII bomb.
With a yield of 9.5 tons TNT, the Grand Slam is 1579× smaller than the Hiroshima bomb. It is a conventional high-explosive weapon that releases its energy through chemical reactions, not nuclear processes.
Grand Slam Blast Effects
The table below shows the calculated radius of each effect zone for an air burst (optimal altitude, maximum blast spread) and a surface burst (ground level, with massive radioactive fallout). Formulas are scaling laws from The Effects of Nuclear Weapons (Glasstone & Dolan, 1977).
| Effect zone | Air burst | Surface burst |
|---|---|---|
| Fireball radius | 0.02 km | 0.02 km |
| Severe blast (20 PSI) | 0.10 km | 0.06 km |
| Moderate blast (5 PSI) | 0.22 km | 0.12 km |
| Light blast (1 PSI) | 0.63 km | 0.35 km |
| 3rd-degree thermal burns | 0.10 km | 0.06 km |
| 2nd-degree thermal burns | 0.18 km | 0.11 km |
| Lethal fallout zone | minimal | ~1.9 km |
All values are 1-D ground-distance estimates from the detonation point. Real-world effects depend on terrain, weather, and building construction.
Run the Grand Slam on a City
Use the interactive simulator to detonate the Grand Slam on any city worldwide. Click any location on the map to see the fireball, blast, and thermal radii overlaid on real geography with population-density-based casualty estimates.
🎯 Simulate Grand SlamRelated Weapons
FAQ
How big is the Grand Slam blast radius?
In an air burst, the Grand Slam produces a fireball roughly 0.02 km in radius and a 5 PSI moderate-blast zone of about 0.22 km — the area in which most residential buildings would collapse. The 1 PSI light-damage radius extends to roughly 0.63 km, where windows shatter.
What is the yield of the Grand Slam?
The Grand Slam has a yield of 9.5 tons TNT of TNT equivalent. That is 1579× smaller than the Hiroshima bomb.
Is the Grand Slam bigger than the Hiroshima bomb?
The Hiroshima bomb (Little Boy) had a yield of approximately 15 kilotons. The Grand Slam at 9.5 tons TNT is 1579× smaller than the Hiroshima bomb.