This calculator designs passive harmonic filters to mitigate harmonics in VFD-rich environments, reducing total harmonic distortion (THD). Input system parameters (voltage, power, frequency), harmonic details (order, initial/desired THD), and filter type (tuned or detuned) to calculate filter components (inductance, capacitance) and estimated THD reduction. The tool is useful for power quality engineers ensuring compliance with IEEE 519 standards.