Beyond rough "what if" estimation, in vitro dissolution is infrequently predicted. The objective was to assess the predictability of a powder dissolution model with a single diffusion layer thickness model, where dissolution of various drugs was facilitated by several surfactant micelles. Powder dissolution of three poorly water soluble drugs (i.e., posaconazole, ritonavir, and griseofulvin) was measured into buffer, as well as four surfactant solutions [i.e., sodium lauryl sulfate (SLS), polysorbate 80 (PS80), polyoxyethylene (10) lauryl ether (POE10), and cetyltrimethylammonium bromide (CTAB)]. Drug solubility, micelle sizing, and powder sizing were also performed. Prediction of drug dissolution employed the film dissolution model, applied to spherical drug particle fractions of the percent weight particle size distribution, and with a surfactant-mediated dissolution component. There were two competing models for diffusion layer thickness: fixed thickness (i.e., h