The practical applications of studies related to constant amplitude mode I loading are somewhat limited in situations where more than one mode exists. So, criteria, rules and laws for these situations have to be validated with experiments. This paper extends previous results by the authors for mixed‐mode I and II fatigue loading. An effective stress intensity factor range which considers crack closure and crack surface interference is described for the analysis of a crack under mixed‐mode I and II fatigue loadings, and this factor is assessed from experimental results.