A method and an arrangement for determining elevator data based on the position of an elevator car of an elevator system includes the elevator car having a flag reading sensor, the elevator car being movably arranged in a hoistway and can be moved by a drive with a suspension rope over a traction sheave, and the elevator car can be stopped at a plurality of stopping positions of the hoistway. Each stopping position has a flag marker with a flag height. Movement of the elevator car is determined by a control unit connected to an encoder at the traction sheave. When leaving a stopping position, the travelled distance of the elevator car between the stopping position and a flag edge is measured and a stopping inaccuracy is determined by the control unit.