The energy penalty for bilayer phase domain interfaces, line tension, is an important quantity for describing the phase domain size transition from the nanometer scale to the micrometer scale and larger. We connected pairwise lipid interaction energies in ternary lipid mixtures with experimentally measured line tensions by using the compositional differences between coexisting liquid-disordered (Ld) and liquid-ordered (Lo) phases known from phase diagrams. Using a mean-field theory model, we developed a computational procedure to map out Ld + Lo phase boundaries and thermodynamic tielines based on a set of pairwise interaction energies. We find that experimentally measured Ld/Lo line tension can be effectively modeled by the sum of pairwise interactions at the interface. This result indicates that pairwise lipid interactions make a major contribution to line tension.