The accuracy of results from Monte Carlo ray-tracing analysis significantly depends on the input values of the optical properties of the various package components. One important piece of input information is the phosphor particle MFP (mean-free-path), which is not easily determined. This study introduced a method to determine the MFP by matching the experimental results with optical ray-tracing analysis at a wavelength beyond the phosphor excitation range. Using these experiment values for MFP in an optical ray-tracing analysis of a white LED package showed an excellent match with measured results for light output and chromaticity.