The Heat of Reaction Calculator determines the enthalpy change (ΔH) of a chemical reaction using either the standard enthalpies of formation method or the calorimetry method. In the formation method, it calculates the heat of reaction from the difference between the total enthalpies of products and reactants, based on their standard formation values. In the calorimetry method, it uses the formula q = m · c · ΔT, where m is the mass, c is the specific heat capacity, and ΔT is the temperature change. The calculator provides results in both joules (J) and kilojoules (kJ), clearly indicating whether the reaction is exothermic (releases heat) or endothermic (absorbs heat).