Procedures are outlined for calculating the heats of explosion (HEX) of neat energetic materials or propellant/explosive formulations using thermochemical computer codes. The "exact" method and three approximate techniques are described; the approximate techniques either eliminate the need to sum the internal energies of the predicted products, or eliminate the need to specify a freeze-out temperature. The various techniques are illustrated for HMX and a nitrocellulose/nitroglycerine (NC/NG) mixture.