A method, computer program, control and / or regulating device for operating an internal combustion engine

A method of operating an internal combustion engine (10), wherein in the determination of a pressure (ps) located in an upstream of an intake valve (22) region (20) comprises a fresh air charge (rl) of a combustion chamber (16) or (for the determination of the fresh air charge rl) of the combustion chamber (16) of the pressure (ps) in the (upstream of the intake valve 22) located region (20) is taken into account, wherein (a rotation speed in the determination nmot) of a crankshaft (18) of the internal combustion engine (10) takes into account is, wherein the fresh air charge (rl) and the pressure (ps) by means of thermodynamic equations and / or by means of flow equations to at least one discrete point in time (72) during a working cycle of the internal combustion engine (10) is calculated (66), wherein a in the calculation after closing of the intake valve (22) in the combustion chamber (16) any residual gas (m_rg) is taken into account, characterized in that the temperature (T_bres) of the combustion chamber (16) bef indlichen gas mixture based on the mixture formula taking into account the mass fractions (m_rgreasp, m_fg) is determined reaspirativen of the residual gas and fresh air, and the respective temperatures (T_rgreasp, T_fg).