The Bond Energy Calculator determines the heat of reaction (ΔH) using the bond energies of reactants and products. The formula used is ΔH = Σ(bonds broken) − Σ(bonds formed), where breaking bonds requires energy and forming bonds releases energy. This tool helps identify whether a chemical reaction is endothermic (absorbs heat) or exothermic (releases heat), with results shown in kilojoules per mole (kJ/mol).