Capacitive Reactance Formula

The capacitive reactance is defined as the opposition offered by capacitor against the current flow. From Ohm’s law, we know that current flowing through any dc circuit is inversely proportional to the resistance. In case of capacitive circuits, the reactance plays the same role. The formulas for capacitive reactance are:

Capacitive reactance formulas
In terms of frequency Xc =
1 / 2πfC
In terms of angular frequency Xc =
1 / ωC
Capacitve impedance Zc = -jXc


f = frequency

C = capacitance

Capacitive reactance calculator

Check any of two boxes and enter known parameters in front of checked boxes.


The capacitive reactance varies inversely with the frequency. The higher the frequency the lower the reactance and the lower the frequency the higher will be the reactance. The curve below better illustrates this behavior:


There are two interesting things one should know:

At f = 0 Hz the Xc is infinite. That is the reason a capacitor appears open to direct current (DC).

At f = ∞, Xc = 0.

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