Mechanical losses in electric machines can contribute significantly to overall system losses in an electric drive. With an Interior Permanent Magnet (IPM) machine, measuring mechanical losses is difficult without an un-magnetized rotor. Even with an un-magnetized rotor, physical testing can be time consuming and expensive. This paper presents a theoretical model of mechanical drag in an electric machine. The model was built using calculations for bearing, seal, and windage drag. This model was compared to experimental results and a sensitivity study was completed to understand inaccuracies in the model. Based on this information, the model was modified to better represent the physical system. The goal of this work is to understand the contributors to mechanical drag, to be able to estimate mechanical losses without physical testing, and to evaluate design choices that could reduce mechanical losses.