Work out binding energy per nucleon instantly with clear inputs, formula shown and shareable results.
Dividing total binding energy by mass number gives the energy holding each nucleon, and this is what governs whether fusion or fission releases energy. Iron-56 peaks at 8.79 MeV per nucleon, so lighter nuclei gain by fusing and heavier ones by splitting - both moving towards that maximum.
Binding energy per nucleon
BE/A = total binding energy / mass number
Energy conversion
1 MeV = 1.602e-13 J
Because the strong force saturates at short range while electrostatic repulsion between protons keeps growing with size. The balance turns over around A = 56-62.
Stars gain energy fusing up to iron and no further. Beyond that, fusion costs energy, which is why iron cores collapse into supernovae.