Castle Bravo vs Ivy Mike
Nuclear weapon side-by-side comparison
Castle Bravo
USA · 1954 · thermonuclear
15 Mt
Most powerful US nuclear test.
Ivy Mike
USA · 1952 · thermonuclear
10.4 Mt
First hydrogen bomb test.
Verdict
The Castle Bravo is 1.4× more powerful than the Ivy Mike 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 | Castle Bravo | Ivy Mike |
|---|---|---|
| Yield | 15 Mt | 10.4 Mt |
| Fireball radius | 6.79 km | 5.86 km |
| Severe blast (20 PSI) | 11.51 km | 10.20 km |
| Moderate blast (5 PSI) | 24.60 km | 21.80 km |
| Light blast (1 PSI) | 69.98 km | 62.01 km |
| 3rd-degree thermal burns | 34.54 km | 29.72 km |
| 2nd-degree thermal burns | 61.86 km | 53.23 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 Castle Bravo is 1,000× more powerful than the Hiroshima bomb. The Ivy Mike is 693× more powerful.
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FAQ
Is the Castle Bravo bigger than the Ivy Mike?
Yes. The Castle Bravo (15 Mt) is 1.4× more powerful than the Ivy Mike (10.4 Mt).
What is the blast radius of the Castle Bravo compared to the Ivy Mike?
For an air burst, the Castle Bravo produces a 5 PSI moderate-blast radius of 24.60 km, versus 21.80 km for the Ivy Mike. Severe blast (20 PSI): 11.51 km vs 10.20 km. 3rd-degree thermal burns: 34.54 km vs 29.72 km.
How many people would die from a Castle Bravo compared to a Ivy Mike?
Detonated over a typical dense city center (8,000 people/km²), the Castle Bravo would cause an estimated 9,203,897 immediate fatalities. The Ivy Mike would cause an estimated 7,227,591. Real numbers depend on time of day, sheltering, weather, and altitude of detonation.
How do the Castle Bravo and Ivy Mike compare to the Hiroshima bomb?
The Castle Bravo is 1,000× more powerful than the Hiroshima bomb (Little Boy, 15 kt). The Ivy Mike is 693× more powerful than the Hiroshima bomb.