Calculate the Q-value of any nuclear reaction to determine if it releases or absorbs energy.
Enter atomic masses of reactants and products. Q = (sum of reactant masses − sum of product masses) × 931.494 MeV.
The Q-value of a nuclear reaction is the net energy released or absorbed. It equals the difference in total mass between the reactants and products, converted to energy units. A positive Q means the reaction is exothermic (releases energy), while a negative Q means it's endothermic (requires energy input to proceed).
For example, the deuterium-tritium fusion reaction (D + T → He-4 + n) has a Q-value of about +17.6 MeV — one of the highest Q-values per nucleon of any fusion reaction, which is why it's the primary candidate for fusion power reactors.