Hi, this may be a very trivial question but, When calculating energy, is it BE(products) - BE(reactants) or is it the other way round? I have been solving questions and the solutions were products - reactants for some and reactants - products for some. Also for mass defect , is it mass ( products ) - mass ( rxts ) or again is it the other way round ? Does it change for fusion/fission ? Edit: I think I got it, if energy is released then mass defect = (mass reactants) - (mass products) , if it is energy absorbed it is the other way round. For energy it is BE(Products)-BE(reactants) for energy released and the other way round for energy absorbed. Am I right?