<p>The paper presents a numerical analysis of the free transverse vibration frequencies of the isotropic pentagonal plates of various thicknesses with one rigidly fixed edge and other edges free. The analysis is based on the finite element method and the reduced formula for calculating the frequencies of free vibrations of the isotropic pentagonal plate with free edges. The limits of application of the reduced formula are established, the coefficients of vibration mode and boundary conditions for the plates with various thickness-to-side ratios are determined. Deviations between the frequencies obtained using the finite element method and the reduced formula are identified. Free longitudinal vibration frequencies of the plates of various thicknesses are computed using the finite element method. Transverse and longitudinal vibration modes are obtained.</p>