Little Boy vs W76
Nuclear weapon side-by-side comparison
Little Boy
USA · 1945 · pure fission
15 kt
Hiroshima bomb.
W76
USA · 1978 · thermonuclear
100 kt
Common SLBM warhead.
Verdict
The W76 is 6.7× more powerful than the Little Boy 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 | Little Boy | W76 |
|---|---|---|
| Yield | 15 kt | 100 kt |
| Fireball radius | 0.43 km | 0.91 km |
| Severe blast (20 PSI) | 1.18 km | 2.20 km |
| Moderate blast (5 PSI) | 2.52 km | 4.71 km |
| Light blast (1 PSI) | 7.16 km | 13.39 km |
| 3rd-degree thermal burns | 2.03 km | 4.43 km |
| 2nd-degree thermal burns | 3.64 km | 7.93 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 Little Boy is 1× more powerful than the Hiroshima bomb. The W76 is 7× more powerful.
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FAQ
Is the Little Boy bigger than the W76?
No. The W76 (100 kt) is 6.7× more powerful than the Little Boy (15 kt).
What is the blast radius of the Little Boy compared to the W76?
For an air burst, the Little Boy produces a 5 PSI moderate-blast radius of 2.52 km, versus 4.71 km for the W76. Severe blast (20 PSI): 1.18 km vs 2.20 km. 3rd-degree thermal burns: 2.03 km vs 4.43 km.
How many people would die from a Little Boy compared to a W76?
Detonated over a typical dense city center (8,000 people/km²), the Little Boy would cause an estimated 96,377 immediate fatalities. The W76 would cause an estimated 337,095. Real numbers depend on time of day, sheltering, weather, and altitude of detonation.
How do the Little Boy and W76 compare to the Hiroshima bomb?
The Little Boy is 1× more powerful than the Hiroshima bomb (Little Boy, 15 kt). The W76 is 7× more powerful than the Hiroshima bomb.