We use single nanoparticle luminescence microscopy to determine a distribution of individual chromophores present in porous Si nanoparticles. From these distributions, we determine the average number of emitting chromophores in each nanoparticle and the fluorescence emission count rate of a single chromophore within the porous silicon nanoparticle. We also show that the same size nanoparticles prepared under two different electrochemical conditions have different fluorescence peak maxima, and exhibit different chromophore number distributions, consistent with the quantum confinement model for the luminescence in porous silicon.