Cochlear amplifier gain in humans and mice was quantified using a phenomenological model of DPOAE generation. The model consisted of a positive feedback loop to represent the cochlear mechanical amplifier; cochlear nonlinearity was represented by a first or second order Boltzmann function (order of the function was species-dependent). Cochlear nonlinearity was separated from the feedback loop based on the respective stimulus-level dependent dominances of the feedback loop and nonlinearity at low and high stimulus levels. The feedback parameter, Γ, was defined by a up to a five term exponential and a nonlinear least-squares fit of this equation to DPOAE data-derived values of Γ generated a stimulus-level dependent equation for Γ. DPOAE I/O functions were obtained over a range of stimulus levels and frequencies. The feedback gain, Γ, at 0 dB SPL, was used as an estimate of the cochlear amplifier feedback gain. Results showed gain to be frequency-independent, with absolute gain higher in mice than in humans for cochlear place-equivalent frequencies.