Our computational approach involves the calculation of both the covalent and non-covalent binding free energy contributions of inhibitors to the M pro target. From an in silico perspective, understanding these two binding contributions is important for the efficient optimization and design of potent compounds. For estimating the noncovalent binding free energy contributions of the inhibitors to the M pro target, we employed equilibrium binding absolute free energy simulations using both non-enhanced and enhanced sampling methods. Our results indicate that enhanced sampling methods via the replica exchange algorithm yield binding free energy estimates that are better converged and have a lower standard deviation than the non-enhanced methods. Hydrogen bonding and dispersion forces are significant contributors to the non-covalent binding free energy of the inhibitors to the M pro target. Our calculation of the covalent binding free energy contribution of the inhibitors to the M pro suggest that the reaction is moderately exergonic, which is in line with the reversible character of these inhibitors as reported by experiment. We observe different covalent binding energies for M pro inhibitor compounds sharing a common aldehyde warhead group, suggesting that multiple factors other than warhead type influence the binding energetics of reversible covalent inhibitors.