Fat Man vs MOAB (Mother of All Bombs)
Nuclear weapon side-by-side comparison
Fat Man
USA · 1945 · pure fission
21 kt
Nagasaki bomb.
MOAB (Mother of All Bombs)
USA · 2003 · conventional
11 tons TNT
GBU-43/B Massive Ordnance Air Blast.
Verdict
The Fat Man is 1,909× more powerful than the MOAB (Mother of All Bombs) by yield. Both weapons are described in detail below, with side-by-side blast and thermal radii, casualty estimates at a reference urban density, and historical context.
Blast & thermal effects (air burst)
| Effect zone | Fat Man | MOAB (Mother of All Bombs) |
|---|---|---|
| Yield | 21 kt | 11 tons TNT |
| Fireball radius | 0.49 km | 0.02 km |
| Severe blast (20 PSI) | 1.32 km | 0.11 km |
| Moderate blast (5 PSI) | 2.81 km | 0.23 km |
| Light blast (1 PSI) | 8.00 km | 0.66 km |
| 3rd-degree thermal burns | 2.33 km | 0.11 km |
| 2nd-degree thermal burns | 4.18 km | 0.19 km |
Casualty estimate (dense urban target)
Estimated immediate fatalities if each weapon air-bursts over a city center with a population density of about 8,000 per km² (representative of dense urban cores like Manhattan or central Paris):
Real casualties depend strongly on time of day, sheltering, weather, and altitude of detonation. See the methodology page for the underlying formulas.
Hiroshima reference
The Hiroshima bomb (Little Boy) had a yield of approximately 15 kilotons. The Fat Man is 1× more powerful than the Hiroshima bomb. The MOAB (Mother of All Bombs) is 1363.6× smaller.
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FAQ
Is the Fat Man bigger than the MOAB (Mother of All Bombs)?
Yes. The Fat Man (21 kt) is 1,909.1× more powerful than the MOAB (Mother of All Bombs) (11 tons TNT).
What is the blast radius of the Fat Man compared to the MOAB (Mother of All Bombs)?
For an air burst, the Fat Man produces a 5 PSI moderate-blast radius of 2.81 km, versus 0.23 km for the MOAB (Mother of All Bombs). Severe blast (20 PSI): 1.32 km vs 0.11 km. 3rd-degree thermal burns: 2.33 km vs 0.11 km.
How many people would die from a Fat Man compared to a MOAB (Mother of All Bombs)?
Detonated over a typical dense city center (8,000 people/km²), the Fat Man would cause an estimated 120,341 immediate fatalities. The MOAB (Mother of All Bombs) would cause an estimated 823. Real numbers depend on time of day, sheltering, weather, and altitude of detonation.
How do the Fat Man and MOAB (Mother of All Bombs) compare to the Hiroshima bomb?
The Fat Man is 1× more powerful than the Hiroshima bomb (Little Boy, 15 kt). The MOAB (Mother of All Bombs) is 1363.6× smaller than the Hiroshima bomb.