RLC Impedance Calculator

Electrical impedance describes how strongly an alternating-current circuit opposes current. Unlike resistance alone, impedance includes energy storage in inductors and capacitors, so both its magnitude and phase depend on frequency. In a series RLC circuit the resistance, inductive reactance, and capacitive reactance combine as a complex quantity. This calculator reports the magnitude in ohms and the phase angle in degrees, then applies Ohm's law to estimate RMS current. Inductive reactance is XL = 2πfL. It increases in direct proportion to frequency because a rapidly changing current creates a larger opposing voltage in an inductor. Capacitive reactance is XC = 1 / (2πfC). It decreases as frequency rises because a capacitor passes rapid changes more readily. The net series reactance is XL minus XC. The impedance magnitude is the square root of R squared plus that net reactance squared. The phase angle is the arctangent of net reactance divided by resistance. A positive result describes an inductive circuit, where current lags voltage. A negative result describes a capacitive circuit, where current leads voltage. When XL and XC are equal, their effects cancel, the angle is zero, and ideal series impedance equals resistance. This condition is resonance and usually produces the largest current for a fixed source voltage. RMS voltage is used because it expresses the heating-equivalent value of an AC waveform. Dividing RMS voltage by impedance magnitude gives RMS current for an ideal sinusoidal steady state. The calculation does not model switching transients, nonlinear cores, dielectric loss, winding resistance, or frequency-dependent source impedance. Those effects matter in physical circuits and should be included when selecting parts or validating a design. The input fields use common engineering units: resistance in ohms, inductance in millihenries, capacitance in microfarads, frequency in hertz, and voltage in volts RMS. Values are converted to henries and farads before calculation. Use the result to verify homework, estimate current, compare component combinations, or choose a test frequency. For mains-powered or high-energy circuits, treat the output as an analytical estimate and follow appropriate electrical safety practices, component ratings, and measurement procedures.