In this article we use statistical behavior of molecules to calculate the speed of a gas which is pumped from a helicoid multi-groove molecular pump and from a turbomolecular pump. Thus, we obtain the compression and the pumping speed of the pumps, through very simple formulae, where the main independent variable is the angle between the helixes for the helicoid multi-groove molecular pump and the angle between the blades for the turbomolecular pump. Furthermore we obtain the reconciliation of views of Gaede and Becker from one side and of Kruger and Shapiro from the other, through the geometry of the pumps and their peripheral losses.