A numerical method for determination of particle size distribution of limestone was developed based on a pH-stat dissolution measurement. The method originated from the calculation of the layer thickness distribution of plane limestone but was expanded to the spherical particles. It was shown that the method can closely reproduce a known particle size distribution and the calculated particle size distribution is comparable with that obtained from a gravity sedimentation analysis. The evaluation of the method indicated that the data sampling and the parameters in the dissolution model are critical in applying the method.