Method for operating an internal combustion engine

In the operation of the internal combustion engine, air quantity of the combustion chamber (rl) is calculated taking into account the pressure (ps) in the intake passage. The charged air amount (rl), and the crankshaft rotational speed (nmot) as an input value, based on the model (A) having a ratio of the pressure in the intake passage (22) in respect to ambient pressure (pu) (ps) it is proposed to be calculated.