The scope of the paper is the experimental determined of the quality factor near resonance and antiresonance frequencies for a six unloaded unclamped piezoceramic plates (PZT5-H) samples. The electromechanical coupling coefficient (EMCC) of the samples are predicted using theoretical approach. The total losses tangent factor of the plate's materials PZT-5H was estimated from the variation of driving point electrical impedance over the interested frequency band rather than the sensitivity of each plate within this band. Experiments are conducted to verify the theoretical results with good agreement. dependence of the resonant and ant resonant frequencies and the electromechanical-coupling coefficient on the relative size of plate is analyzed. These results suggest that driving piezoelectric devices at anti-resonance mode may be an alternative in order to get improved efficiency in piezo device operation.