The Binding Energy Calculator computes the total binding energy of a nucleus using the mass defect and Einstein’s equation Eb=Δm c2E_b = \Delta m \, c^2Eb​=Δmc2. By entering the mass defect, the calculator determines the energy holding the nucleus together. Optionally, dividing by the number of nucleons gives the binding energy per nucleon. This tool is useful for nuclear physics, understanding nuclear stability, and studying fission or fusion reactions.