• calculate the number of CFUs in the original sample number of CFUs per ml of sample = number of colonies (30-300 plate) X the dilution factor of the plate counted For a more accurate count it is advisable to plate each dilution in duplicate or triplicate and then find an average count.• calculate the number of CFUs in the original sample number of CFUs per ml of sample = number of colonies (30-300 plate) X the dilution factor of the plate counted For a more accurate count it is advisable to plate each dilution in duplicate or triplicate and then find an average count