Capacitive reactance is the opposition presented to alternating current by a capacitor, and it is measured in ohms of reactance like resistance. It is a key quantity in all forms of electrical and electronic circuits, and it is used to compute amplitude and phase changes of sinusoidal alternating current going through a circuit element. Capacitive reactance is different from resistance, but it is measured in ohms just the same. The reactance of a capacitor depends on the value of the capacitor and the frequency of operation. The higher the frequency, the smaller the reactance.

The formula for capacitive reactance is Xc = 1 / 2πfC, where Xc is the capacitive reactance in ohms, f is the frequency in Hertz, and C is the capacitance in Farads. The unit of capacitive reactance is Ohms like resistance, and the symbol of capacitive reactance is XC.

Capacitive reactance is important because capacitors are used in many electrical and electronic circuit designs. Being able to calculate the level of reactance is important, and knowing how this reactance affects the current flow with other electronic components is also of great importance.