A prediction tool for the crack propagation is developed by the tearing energy concept and the finite element method. The value of the critical tearing energy, at which the crack propagation starts, is determined for different initial crack sizes. It is shown, that the critical tearing energy is influenced both by the loading rate and temperature and that the time-temperature-shift-principle and the WLF-equation can be applied. A procedure is also introduced to separate the influences of geometry and material on the tearing energy. Finally, the crack propagating load can be calculated for rubber parts by the finite element method and the critical tearing energy. Hereby, the calculated and measured critical loads for crack propagation in a rubber part correspond well.