The effect of swelling in CR-39, during the etching process has been studied using ‘thickness-measurement’ method. The values of the bulk etch-rate ( V B) determined by this method have been corrected in the context of irreversible swelling produced in various CR-39 samples. The results have been compared with those obtained using the ‘mass-measurement’ as well as the ‘fission fragment track diameter’ methods. The values of experimental V B have been obtained by taking the arithmetic average as well as by fitting the Gaussians to the results of a number of CR-39 samples. It is shown that the ‘thickness-measurement’ method is as good as the other methods of determining the bulk etch-rate provided sufficiently large number of CR-39 samples are used for obtaining the mean value from the Gaussian fit of the experimental data.