In this work we propose a simple method to estimate gasoline, gas, and coke yields in the catalytic cracking process. The method requires only experimental information about the variation with time of product yields, which are correlated using a third-order polynomial. Combined cracking and decay constants in the 3- and 4-lump kinetic models reported in the literature are estimated by linear regression analysis using experimental data and the proposed methodology. The kinetic model differential equations were solved using a fourth order Runge-Kutta method in order to evaluate FCC product yield-conversion relationships. The proposed methodology gives accurate predictions of product yields in the FCC process with average deviations less than 3% with respect to experimental data.