The cutting of soft tissue is important from a medical perspective with many different designs of scalpel blades, scissors and punch cutters available. While there is little understanding of the “cutability” of various biological tissues in surgical practice (i.e. the nature of the relationship between the blade and the quality of cut achieved), it is believed that wounds produced by sharper blades heal better and more quickly. From an engineering perspective, little is known about the performance of blade-type cutting surgical instruments and the true meaning of terms such as ‘sharp’ and ‘blunt’ in the context of blade performance. In this study, a simplified model of soft tissue failure, using a strain energy-based model, is developed and validated for the cutting of soft tissue by a single sharp blade. An experimental model is used to study the cutting characteristics of skin under tension. Skin is a highly deformable, viscoelastic, anisotropic material with non-linear stress-strain behaviour. The model minimises the energy lost in remote plastic flow, ensuring that as much as possible of the energy input into the system goes directly into cut formation. Based on results from eight samples, the resistance to fracture of skin was calculated to be 2.79 ± 0.55 kJm-2, which is in good agreement with the literature. The model and experimental technique proposed may help to establish the failure properties of soft tissues under a variety of cutting conditions and could be used to evaluate different cutting instruments and to investigate the quality of surgical techniques.