Ivy Mike vs Castle Bravo
Nuclear weapon side-by-side comparison
Ivy Mike
USA · 1952 · thermonuclear
10.4 Mt
First hydrogen bomb test.
Castle Bravo
USA · 1954 · thermonuclear
15 Mt
Most powerful US nuclear 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 | Ivy Mike | Castle Bravo |
|---|---|---|
| Yield | 10.4 Mt | 15 Mt |
| Fireball radius | 5.86 km | 6.79 km |
| Severe blast (20 PSI) | 10.20 km | 11.51 km |
| Moderate blast (5 PSI) | 21.80 km | 24.60 km |
| Light blast (1 PSI) | 62.01 km | 69.98 km |
| 3rd-degree thermal burns | 29.72 km | 34.54 km |
| 2nd-degree thermal burns | 53.23 km | 61.86 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 Ivy Mike is 693× more powerful than the Hiroshima bomb. The Castle Bravo is 1,000× more powerful.
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FAQ
Is the Ivy Mike bigger than the Castle Bravo?
No. The Castle Bravo (15 Mt) is 1.4× more powerful than the Ivy Mike (10.4 Mt).
What is the blast radius of the Ivy Mike compared to the Castle Bravo?
For an air burst, the Ivy Mike produces a 5 PSI moderate-blast radius of 21.80 km, versus 24.60 km for the Castle Bravo. Severe blast (20 PSI): 10.20 km vs 11.51 km. 3rd-degree thermal burns: 29.72 km vs 34.54 km.
How many people would die from a Ivy Mike compared to a Castle Bravo?
Detonated over a typical dense city center (8,000 people/km²), the Ivy Mike would cause an estimated 7,227,591 immediate fatalities. The Castle Bravo would cause an estimated 9,203,897. Real numbers depend on time of day, sheltering, weather, and altitude of detonation.
How do the Ivy Mike and Castle Bravo compare to the Hiroshima bomb?
The Ivy Mike is 693× more powerful than the Hiroshima bomb (Little Boy, 15 kt). The Castle Bravo is 1,000× more powerful than the Hiroshima bomb.