Fracture toughness, KIC, is an essential material property representing the resistance to crack propagation in the most prevalent opening mode. The fracture toughness should be correspondingly high to prevent premature failure of a material or a thin film with subsequent environmental exposure of the substrate. As a result, toughness is an important safety factor when designing protective coating materials exposed to mechanical loads. The fracture toughness of coatings is typically determined using micromechanical methods due to the small dimensions. The microcantilever bending test should be particularly mentioned here, as it determines the intrinsic KIC without possible substrate influences. This study investigated the influence of the cantilever geometry, particularly the distance between the point of force application and the position of the predefined crack. For this purpose, cathodic arc evaporated TiN was selected as a reference material, and a series of cantilevers were fabricated via focused ion beam (FIB) milling, and subsequently tested with an in-situ indentation stage within the SEM. The calculated fracture toughness was found to be dependent on the distance: as the distance increased, the values decrease to a subsequently constant KIC. In summary, this study discusses failure sources for any over- and under-estimations due to geometrical aspects and provides guidelines for properly conducting and interpreting microcantilever bending tests estimating KIC.