This software computes the magnetic hysteresis curves for an ensemble of Single Molecule Magnets. It has been used to reproduce data recorded on a sample consisting of Fe4 molecules deposited on a superconducting substrate of Pb(111) at temperatures lower than 1 Kelvin. Further details can be found in the article "Quantum dynamics of a single molecule magnet on superconducting Pb(111)" G. Serrano et al., Nat. Mater. (2020).