A macroscopic plasticity constitutive model employing the concept of a contracting Bounding Surface is formulated for plain concrete. The concrete strength fc is the only necessary input material constant. The model is used to predict the stress‐strain relations for uniaxial, biaxial, and triaxial compression states for both monotonic and cyclic loading conditions including post‐failure states for different strength concretes. The results are successfully compared with available experimental data.