This study investigates the relationship between filter inductor impedance and dimensional resonance of MnZn ferrite. Experimental results clarify that multiple factors affect inductor impedance resonances. These can be classified into three factors: the inherent characteristics of a magnetic material, self-resonance due to winding stray capacitance, and winding that acts as a distributed constant line. Next, based on the measurement results, the dimensional dependencies of complex permeabilities (dimensional resonance) and the influence of dimensional resonance on inductor impedance are discussed in detail. Finally, this study verifies that the influence of dimensional resonance on complex permeability can be mitigated, and filter inductor impedance can be increased in the high frequency range by core lamination. All experiments are performed using off-the-shelf magnetic core products.