Abstract Determination of accurate mixed mode stress intensity factors forms the basis for the understanding and analysis of mixed mode fracture. In this context, experimental methods for the measurement of stress intensity factors (SIFs) play a vital role. However, very few strain gage based techniques are available for measurement of mixed mode SIFs KI and KII in isotropic materials. In addition, no useful recommendations on appropriate radial locations of strain gages ensuring accurate SIFs are available in literature. Recently, authors have theoretically proposed a mixed mode strain gage technique and attempted to address the long standing problem of assessment of appropriate strain gage radial locations for the accurate measurement of the SIFs. They have shown that there exist certain gage radial locations called as optimal locations for the accurate measurement of SIFs, which can be easily assessed with their proposed methodology for any mixed mode (I/II) configurations. In the present investigation, experiments were conducted to study the efficacy of the authors' proposed mixed mode strain gage technique and existence and usefulness of the optimal strain gage locations in accurate measurement of SIFs KI and KII. The present experiments were also aimed to show the consequences of placing the gages at invalid or non-optimal gage locations. The experimental results clearly show that highly accurate mixed mode SIFs can be measured using the proposed mixed mode strain gage technique if the gages are pasted at the optimal locations. On the other hand, the results also exposed that highly erroneous and unacceptable measurement of SIFs can result if the gages are located at non-optimal locations. Furthermore, the present results clearly demonstrated the need of knowing the optimal strain gage locations a priori, which can be assessed using the methodology proposed recently by the authors.