The magnetocaloric effect (MCE) of La 1−x Ca x MnO 3 was analyzed when varying the stoichiometry (x=0.2, 0.33, 0.4 and 0.5) and the external applied magnetic field. Simulations were carried out using the Monte Carlo method having a configuration ascribed by the set S z of all-site spin projections, under the Metropolis algorithm. La 1−x Ca x MnO 3 is characterized for three types of magnetic ions corresponding to Mn 4+ (S=3/2), which are bonded to Ca 2+ , and Mn 3+ (e g ) and Mn 3+ (e g′ , S=2), which are both bonded to La 3+ . Different interactions must be considered depending on the type of interacting ions. The entropy change ΔS in an isothermal process as well as the temperature change ΔT in an adiabatic process was determined with this model. Both ΔS and ΔT show stoichiometry-dependent maximums near the paramagnetic–ferromagnetic transition temperature (T C ), confirming the order–disorder change at this temperature. The strong dependence in La 1−x Ca x MnO 3 of the MCE on the stoichiometry and the external magnetic field makes this phenomenon important for different technological applications, particularly in refrigeration.