During a period of the last ten years a new model has been developed at SwereaKIMAB that is able to predict the fatigue properties of tool steels based on measured carbide and inclusion distributions. The model has been programmed into software named FATSIMR. Lately, effects such as notch effect and surface roughness have been added to the model enabling it to predict the fatigue properties of actual tool designs. In the presence of a notch the software takes into account the decrease in stressed volume and thereby the decreased probability of a defect present in the most stressed part. As an upper bound the software estimates the intrinsic fatigue strength of the steel matrix. In this presentation the model is presented and examples are given on how the software can be applied on various high stressed tooling components.