Membrane reactors (MRs) are often used to carry out equilibrium limited reactions. This is because the thermodynamic equilibrium is a strong constrain for traditional systems. Even with very active catalysts, traditional reactors (TRs) cannot give conversions higher than those allowed by the thermodynamic equilibrium. On the contrary, MRs are able to shift the equilibrium of a traditional system owing to the removal of at least one reaction product that takes place simultaneously to the reaction. In this work, a simplified method for the calculation of limit conversion in MR is discussed and compared with literature methods. The typical method for calculating equilibrium conversions in TR is also discussed. It has been demonstrated that the simplified method applied to two reaction systems gives fast predictions of the limit conversion for MR.