A simple model is presented that uses the concept of helicity balance to predict the toroidal loop voltage of reversed field pinches (RFP’s). Data from the RFP’s at Culham [Plasma Phys. Controlled Fusion27, 1307 (1985)] are used to calibrate and verify the model. The model indicates that most of the helicity dissipation occurs in edge regions that are outside the limiters or in regions where field lines contact the walls. The value of this new interpretation to future RFP and spheromak experiments is discussed.