This paper presents a streamlined method developed to calculate the complete material balance for countercurrent washing on a belt filter, after once a washing-loss curve has been defined. This curve is relatively easy to obtain from pilot-plant or full-scale operation. It can even be determined from a laboratory test that simulates the given conditions and duplicates the cake thickness and washing rate for the belt filter. This discussion derives equations for a belt filter having five countercurrent stages. The calculation method may be readily extended to handle any number of stages. The following topics are detailed: the basic model; auxiliary normalized concentrations; final form of the technique; an exam of the five-stage washing setup; advantages of the new method.