The glass forming ranges of the ternary Al-Mg-Y and Al-Ni-Y systems have been predicted and compared with experimental measurements. A thermodynamic method (CALPHAD method) has been used to obtain T_o curves of five bounding binary systems, Al-Ni, Ni-Y, Y-Al, Al-Ni and Ni-Y, and ternary Al-Mg-Y and Al-Ni-Y systems. Glass transition temperature T_g in these systems has been approximated by crystallization temperature T_x, which was derived from the relationship with hole formation enthalpy. Based on the magnitude between T_o and T_g, the glass forming range has been determined. The range has been calculated to be rather wide because of the upper limit concept for T_g. This approach can be used as a guide to predict the glass forming range of binary, ternary and even multicomponent systems.