The Tsar Bomba differs from its parent design – the RN202 – in several places. The Tsar Bomba was a three-stage bomb with Trutnev-Babaev second- and third-stage design, with a yield of . This is equivalent to about 1,570 times the combined energy of the bombs that destroyed Hiroshima and Nagasaki, 10 times the combined energy of all the conventional explosives used in World War II, one quarter of the estimated yield of the 1883 eruption of Krakatoa and 10% of the combined yield of all nuclear tests to date. A three-stage hydrogen bomb uses a fission bomb primary to compress a thermonuclear secondary, as in most hydrogen bombs, and then uses energy from the resulting explosion to compress a much larger additional thermonuclear stage. There is evidence that the Tsar Bomba had several third stages rather than a single very large one.