Reactance Calculator (Inductive & Capacitive)

The reactance calculator computes inductive reactance (XL) and capacitive reactance (XC) for given component values at a specified frequency. Reactance is the frequency-dependent opposition that inductors and capacitors present to alternating current (AC), distinct from resistance which is independent of frequency. Understanding reactance is fundamental to AC circuit analysis, filter design, impedance matching, and power factor correction.

Inductive reactance XL = 2πfL increases linearly with frequency. At DC (f = 0), an inductor is a short circuit (XL = 0). As frequency increases, an inductor increasingly resists current flow, eventually appearing as an open circuit at very high frequencies. This property makes inductors effective at blocking high-frequency noise while passing DC and low-frequency signals.

Capacitive reactance XC = 1/(2πfC) decreases inversely with frequency. At DC, a capacitor is an open circuit (XC → ∞). As frequency increases, the capacitor passes current more easily, appearing as a short circuit at very high frequencies. This makes capacitors effective at blocking DC while passing AC signals — the principle behind coupling capacitors in amplifiers.

The net reactance X = XL - XC determines the overall reactive character of a circuit. When X > 0, the circuit is inductive (current lags voltage). When X < 0, the circuit is capacitive (current leads voltage). When X = 0, the circuit is at resonance — the operating frequency equals the resonant frequency 1/(2π√(LC)).

Power engineers use reactance calculations for power factor correction. Capacitor banks are added to industrial facilities to offset inductive reactance from motors and transformers, bringing the power factor closer to unity. RF engineers use reactance to design matching networks, transforming impedances to maximize power transfer.

This calculator accepts frequency in Hz, inductance in millihenries (mH), and capacitance in microfarads (µF). It simultaneously displays XL, XC, net reactance, and the resonant frequency for the given L and C values.