Among techniques for the determination of the mode I stress intensity factors (SIFs), strain gage procedures are the simplest and most straightforward. We report here on an experimental investigation of the determination of opening mode stress intensity factors using the single strain gage method. Our approach overcomes certain drawbacks and greatly widens the applicability of strain gage methods in the determination of static SIFs of complex configurations. The approach was tested through experiments on specimens of finite width and finite height edge-cracked plates (fully finite plates) subjected to tensile stress. We compared the experimentally determined mode I stress intensity factors of fully finite plates with the computed values using finite element analysis, obtaining good agreement between the present approach and computed values.