RLC Impedance Calculator

About this calculator

In a series RLC circuit, the total opposition to alternating current — the impedance — combines resistance with reactance: Z = √(R² + (X_L − X_C)²), where the inductive reactance X_L = 2πfL grows with frequency and the capacitive reactance X_C = 1/(2πfC) shrinks with frequency. At the resonant frequency f₀ = 1/(2π√(LC)), the two reactances cancel exactly, leaving impedance at its minimum (equal to just R) and current at its maximum.

Electrical and electronics engineers use this calculation to design radio tuners, band-pass filters, and oscillator circuits, and to predict how a circuit responds across a range of AC frequencies. Enter the resistance, inductance, capacitance, and operating frequency to find the reactances, total impedance, and resonant frequency of the circuit.