The thermodynamic properties and phase equilibria of the Cu-Hf binary system with five intermetallic compounds were studied by experiments, first-principles calculations and CALPHAD modeling. The experimental investigations included differential thermal analysis, scanning electron microscopy, energy dispersive X-ray microanalysis and micro-X-ray diffraction focusing on the 30-60 at.% Hf composition range to determine the invariant reaction temperatures. Cu10Hf7 was confirmed to melt incongruently. The enthalpies of formation of all five binary Cu-Hf compounds were predicted through first-principles calculations. The atomic configuration of one of the compounds, Cu51Hf14, was postulated through systematic first-principles calculations with 65 atoms instead of 68 atoms, denoted by hp68 in the literature. The thermodynamic description of the Cu-Hf binary system was then obtained from the new experimental data and first-principles calculations. (c) 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.