A portable cement mixing system uses ingredients such as cement, water and sand in predetermined quantities. A digital controller coordinates all of the operating elements of the apparatus for the entire mixing process and stores mixing programs relative to the mixing process for a variety of cements which includes the various ingredient quantities. Separate storage containers each coupled to a conveyors from the container extend to a mixer to transfer that quantity to the mixer for each cement ingredient. The conveyors are operated in sequence by the controller to load the mixer with a predetermined quantity of each of the required ingredients prior to mixing. The mixer and its contents are weighed before and during the transfer of each ingredient to precisely determine and transfer the required amount of each ingredient. After the mixer is loaded with all of the ingredients, the mixer is operated for a predetermined length of time.