How big is a nuclear blast radius? - Answers

Little Boy was the nuclear bomb detonated over Hiroshima. It used uranium and had an explosive blast equivalent to 12,500 tons of TNT. A 1 megaton hydrogen bomb, hypothetically detonated on the earth's surface, has about 80 times the blast power of that 1945 explosion. Considering the tonnage of a bomb to be contant, The blast radius varies dependent on whether it is a ground burst or an airburst. Further, the height of the airburst above ground affects the radius too. At a height of 1900 feet above ground, Little Boy produced a blast radius of 1 mile; an area of some 4.7 square miles.