Due to the adverse effect that distortion has on assembly fit-up and fabrication costs in welded structures, the ability to predict dimensional changes represents an important engineering concern. While distortion can be analyzed using a full three-dimensional (3D) finite element (FE) model, this often proves to be computationally expensive for medium and large structures. In comparison, a two-dimensional (2D) FE model can significantly reduce the time and effort needed to analyze distortion though such analyses often have reduced accuracy. To address these issues, a 3D plane stress model using shell meshes based on the shrinkage volume approach is proposed. By inversing the plastic shrinkage zone geometry, an eccentric loading condition and equivalent plane stress representation can be developed and used to predict distortion in butt welded plates using an isothermal model. The model was validated using deflection data from welded plates and found to provide good accuracy over the range of thicknesses considered. Results obtained from welding of a large containment tank are also presented and further confirm the utility of the method.