A software energy estimation methodology is presented that avoids explicit characterization of instruction energy consumption and predicts energy consumption to within 3% accuracy for a set of benchmark programs evaluated on the StrongARM SA-1100 and Hitachi SH-4 microprocessors. The tool, JouleTrack, is available as an online resource and has various estimation levels. It also isolates the switching and leakage components of the energy consumption. Keywords Software energy, leakage estimation, instruction energy