To find the total binding energy Use this formula: B= (number of neutrons)(neutron mass)+ (number of protons)(proton mass) - (Atomic Mass of helium). Then to keep the units correct, multiply that entire expression by 931.5 MeV/u. This is the TOTAL binding energy, and the binding energy per nucleon can be found by dividing the number you calculate above by the total number of protons and neutrons.