The plastic work consumed by the flexible metallic foil during a peel test can contribute significantly to the measured load. It is thus important to be able to quantify it in order be able to make inferences about the adhesion at the interface. Several models have been previously proposed which allow the calculation of the plastic work, based on the modulus and yield stress of the flexible metallic foil, assuming ideal plastic behavior. When testing the adhesion of thermal spray coatings, for example, a stainless steel foil is used which work hardens during peeling. A method is proposed here which allows the calculation of the plastic work during peeling for a work hardening material with experimentally determined stress-strain relationship. The plastic work is calculated by integrating the stress-strain curve for the peeled material numerically. The prediction is then compared with experimentally measured plastic work values for several materials.