The designers, optimizers and maintenance personnel of a wireless sensor network are frequently challenged by system level energy budget considerations. Minimizing the need for battery replacement is often the design goal while ensuring that a balance is maintained between capability and current consumption in order to address application needs. In this paper, a tool is introduced which can be used to calculate the lifetime of a battery operated wireless node. It allows the user to configure different wireless sensor platforms, select a battery of choice, and specify the application which needs to be executed over the configured hardware. As a result, the tool computes an estimate for the expected lifetime of the wireless sensor node. Furthermore, the tool also provides a detailed overview of the energy consumed by each component during a duty cycle. © 2013 IEEE.