Abstract: To transport different oil product in sequence by using the same oil product pipeline may involve generation of flow sections with oil mixtures around the contact areas. Consequently, accurate prediction of the volume of such mixtures is a necessary sector in operation of the oil product pipeline. It is also an essential part for preparation of programs for handling of such mixtures. To obtain the calculation equation for oil mixtures in the Kenya-1 Oil Product Pipeline, actual lengths of oil mixtures generated in multiple operations within a month of the pipeline operation were acquired on site. These data have been organized and analyzed to identify major factors that may affect the length of such oil mixtures. By using Austin & Palfrey Equation, the equation deviated from diffusion theory, the empirical equation from Golmud-Lhasa Oil Product Pipeline and SPS simulation software, the length of oil mixtures have been calculated separately. In addition, these calculation results have been compared with measured values on site. With consideration to the assessment results, causes for differences in calculation equations have been analyzed one by one to clarify the suitability of each individual equation. Eventually, the calculation equation applicable to oil mixtures in the Kenya-1 Oil Product Pipeline can be determined.