Magnetic refrigeration is an alternative cooling technology to vapour compression. Due to the large operating space of magnetic refrigeration devices, modelling is critical to predict results, optimize device parameters and regenerator design, and understand the physics of the system. Modeling requires accurate material data including specific heat, magnetization and adiabatic temperature change, . For a reversible material can be attained directly from measurement or indirectly through calculation from specific heat and magnetization data. Data sets of nine MnFeP1-xAsx alloys are used to compare calculated against measured . MnFeP1-xAsx is a promising first order material because of a tunable transition temperature, low material cost and large magnetocaloric properties. Because MnFeP1-xAsx alloys exhibit thermal hysteresis there are four possible calculation protocols for adiabatic temperature change; , , and . deviates the most from measured data and therefore it is assumed that this case is not representative of the material behavior. Results show and align with measured data as well as . The three protocols that align best with measured data have two consistent errors including a colder peak and a larger . With more data sets and analysis a preferred calculation protocol may be found. / Graduate