The experimental results on the hysteresis loops of magnetic films with perpendicular anisotropy show that the loop is sheared. The shearing of the loops depends strongly on the thickness of the film. This phenomenon was never successfully explained with the particulate model. We use a simple three dimensional particulate model with an effective demagnetizing field to calculate the slope of the perpendicular loops. The calculated results are compared with the experimental results for the CoCr sputtered films. By considering different separation distance of the columns, good agreement is obtained between the calculations and the experimental data for the shearing of the loop.