Abstract: An apparatus for making dilutions of a sample with a diluent to a predetermined dilution factor f by weight of the diluent is disclosed. A scale with TARE capability produces an output signal of the weight W of a sample within a container less the weight of the container. A dilution factor control is provided for setting the predetermined dilution factor f. Means are provided for calculating and storing the value TW=W/f which is the total weight of the sample plus the weight of the diluent which is required to dilute the sample to the predetermined dilution factor f. A pump is connected between a reservoir of diluent and the container for the sample for pumping the amount of diluent into the container which is required to dilute the sample to the predetermined weight dilution factor f. The scale provides a continuous output of the weight W of the sample plus diluent in the container at any instant in time. Means are provided for calculating when TW-W=0.