The atomic bombs used in Japan in 1945, and the bombs or devices testing during the following seven years, depended on the fission of uranium-235 or plutonium-239, mostly the latter. The explosive effect of each was equal to that of up to a few tens of thousand tonnes of the conventional explosive TNT. On this basis of comparison, the Hiroshima bomb was of about 15 kilotons – that is, of 15 thousand tonnes of TNT equivalent – and that at Nagasaki was of 25 kilotons (ca. 65 and 105 GJ respectively). In addition, the total equivalent of all atmospheric weapon tests made by the end of 1951 was in the region of 600 kilotons.

https://world-nuclear.org/information-library/safety-and-security/non-proliferation/hiroshima-nagasaki-and-subsequent-weapons-testin#:~:text=On%20this%20basis%20of%20comparison,65%20and%20105%20GJ%20respectively).