Patient-specific CT-based finite element analysis (FEA) of human bones may aid clinicians in estimating the risk of bone fracture [1]. In these FEAs the heterogeneous distribution of bone ash density (ρash) is correlated to the heterogeneous Young’s modulus of the bone tissue. However, predicting fracture risk by applying phase field models requires the heterogeneous fracture toughness GIc that may be determined by different experimental methods. Due to a lack of standards for determining cortical bone’s fracture toughness, an experimental campaign was undertaken on 53 cortical specimens from two fresh frozen femurs to investigate whether a correlation exists between KIc and ρash. Various experimental techniques were investigated resulting in five different correlations stemming from the various experimental methods. The most suitable one was determined by FE analyses employing phase field methods (PFM). FE results employing PFMs show that the ASTM standard using displacement at force application point is the recommended experimental method for the estimation of KIc perpendicular to osteons’ direction [2]: KIc[MPa√m] = 1.89 (ρash[gr/cc])^1.88, R^2 = 0.5374 GIc[N/m] = 321.94 (ρash[gr/cc])^1.69 The proposed correlations was used in CT-based PFM-FEA to better estimate the risk of hip and humeral fractures.