Thermodynamic calculations and Scheil-Gulliver simulations are used for simulating solidification of gray cast iron, systematically varying the composition around Fe-3.35C-2Si by adding Cr, Ni, Mn, Mo, Cu, S, P, and in some cases, Al, V, and B. By adding Ti and N, the competition between Ti(C,N) and N2-gas precipitation is thoroughly studied. The simulated results are assessed by regression analysis producing many explicit formulae for predicting solidification of gray cast iron. The agreement between thermodynamic calculations and regression formulae is generally very good.