Using the optically pumped variable stripe length technique we demonstrate that, through calibration of measured spontaneous emission spectra, it is possible to determine the total radiative recombination rate for a gain material as a function of the intrinsic quasi-Fermi level separation. Specifically we compare the room temperature optical characteristics of a self-assembled InP/GaInP quantum dot material measured using both optical and electrical pumping. The comparison reveals good agreement between gain and emission spectra measured with the two techniques, for the same inversion, from which we conclude that the carrier distributions in each case are equivalent. The results demonstrate that the optically pumped experiment can provide a good measure of the overall radiative efficiency.