Capacitor Impedance at Frequency

About this calculator

This calculator finds a capacitor's capacitive reactance, Xc = 1 / (2πfC), where f is frequency in hertz and C is capacitance in farads. Reactance is a capacitor's frequency-dependent opposition to AC current — unlike a resistor, it isn't constant: reactance drops as frequency rises, which is exactly why capacitors block DC (f = 0, infinite reactance) but pass high frequencies easily.

Audio engineers use it to design crossover networks that route treble to tweeters and bass to woofers, RF and analog circuit designers use it to size decoupling and filter capacitors for a target cutoff frequency, and electronics students use it to verify hand calculations on AC circuit homework.