It is shown that the simple algebraic equation set that describes the breakage rate-mass (population) balance in a fully mixed grinding mill operating at steady state is readily extended to describe mills with other residence time distributions. The algorithms are simple to program as they do not require the use of the Reid solution to the batch grinding set. and they compute rapidly. The formulation is particularly useful for the large diameter-short length semiautogenous tumbling mills that have residence time distributions close to those expected for a fully mixed system. Examples are given using the complex form of the specific breakage function that is applicable to this type of mill. The algorithms are suitable for the direct applications of the Austin method of allowance for different particle velocities in a mill as a function of particle size.