We present a new equation of state for hard chain fluids. This equation of state is developed by applying an extension of Wertheim’s theory for associating fluids to a nonspherical reference fluid. Since the equation of state is developed in a similar manner to the statistical associating fluid theory (SAFT) we call this improved equation of state SAFT-Dimer (SAFT-D). The equation of state requires only the contact values of the hard sphere and hard disphere site-site correlation functions as input. We compare the compressibility factor from SAFT and SAFT-D with molecular simulation data for flexible hard chains with chain lengths of 16, 51, and 201 segments. The second virial coefficient and compressibility factor from SAFT-D are in better agreement with molecular simulation results than the generalized Flory dimer, TPT2, and Percus-Yevick compressibility equations of state.