The pack-boriding kinetics of SAE 1020 steel has been addressed through utilizing four mathematical approaches in case of the formation of diiron boride layers. The values of boron diffusivities and activation energies in Fe2B were assessed in the interval of 1123 to 1223 K by using four models. Finally, the four models were experimentally verified by comparing the predicted results to the experimental value of Fe2B layer thickness determined at 1198 K for 6 hours. Finally, the simulated layers’ thicknesses agreed with the experimental result. In addition, similarities and differences observed in the models were also discussed.