The relationship between the yield ratio and the material constants, b and N, of the Swift equation for hot-rolled low carbon steels has been established. The yield ratio calculated by using the Swift equation agrees well with an experimentally obtained yield ratio. It was found that the yield ratio decreases with an increasing value of N or with a decreasing value of b. It was also found, however, that high yield strength is associated with small values of both b and N. Therefore, to obtain both high yield strength and low yield ratio, a detailed microstructural control is needed to determine the optimum values of b and N.