A method for real-time calculation of state variables (xM) of a process model on a process computer with a first calculating unit and a process interface, wherein the computer is designed so that at least one state variable of a physical process can be received by the computer using the interface and/or at least one output variable for controlling the process can be issued by the computer, wherein the model is calculated by the first calculating unit with an explicit integration method for determining the state variables. According to this method, a second calculating unit is provided, the model is carried out with the second calculating unit using an implicit integration method essentially simultaneously with the calculation of the model with the first calculating unit and the state variables (xM,i) calculated with the second calculating unit and the implicit method are used as state variables (xM) of the model.