The Portrevin-Le-Chatelier (PLC) effect was analysed quantitatively in the selected AlMg alloys with Mg-content between 2,8-4,6%. The propagation and characteristics of PLC bands were detected by digital image correlation (DIC) technique and the parameters of the bands were evaluated from strain distributions of tensile test specimens. In parallel, stress-strain curves were analysed evaluating stress serrations. The numerically defined parameters of changes in stress and strain were used for characterising the PLC effect on the behaviour of different sheet metals. General statements of literature were numerically proven for the tested materials and the effect of magnesium content on stress amplitude was analysed in detail.