Numerous situations in which particle size must be matched to a predetermined distribution or the distribution of a sample must otherwise be altered. Normally, this alteration requires screening the entire sample into various mesh sizes and recombining to form the desired distribution, or using extensive and time-consuming iterative calculations. A computer program to aid in these calculations was developed by the Bureau of Mines for use on a basic processing system. The program determines the quantity of material that must be added to a sample to adjust its size distribution to approximate that of a standard. Operating in an interactive mode, the program will accept up to 20 size fractions as input or will use a standard sq. rt. of 2 distribution, depending on input commands. Also required as input are the particle size distributions of the standard and the sample to be adjusted, the limit of error on the adjustments, and the mass (in grams) of the sample to be prepared.