Phase diagram calculation of Fe–Ti system is obtained by coupling of CALPHAD with first principle methods. Single Gibbs energy model is used for FeTi to take care of order-disorder transition. First principle calculation shows that Laves phase is ferromagnetic nature with the magnetic moment of 1.417μB which is incorporated in the modelling. For extrapolation to higher order system, Laves phase is mostly expressed with two sublattice model. From crystallographic view, 3 sublattice model is appropriate one for description of Laves phase. Hence, two different models are used for Laves phase. Wagner-Schottky model used to describe the homogeneity region of Laves phase in two sublattice model. Using the first principle method, the energies of formation of unstable end members of FeTi phase and three sublattice model of Laves phase are calculated and incorporated as experimental data in optimisation. Calculated phase diagram and the thermochemical properties using 3 sublattice model of Laves phase shows good agreement with the experimental data. © 2020 Elsevier Ltd