The present work was aimed at investigating the applicability of the proposed correlation equations that link the coefficients of the thin-layer equations. Materials of different properties were chosen and dried in four types of laboratory dryers. The experimental data were approximated applying the commonest thin-layer equations: the Lewis equation, the modified Page's model, and Fick's second law. The best match was achieved with the modified Page's model. The applicability of the stated literature correlations was confirmed. Irrespective of the match between measuring data (X = f(t)) and Lewis equation, the evaluated drying constant K allowed evaluation of the parameters of the employed two-parameter models.