Reactance Calculator
Enter a frequency, capacitance, and inductance to find the capacitive and inductive reactance.
How reactance is calculated
Capacitive reactance (Xc) is the opposition a capacitor presents to AC current, calculated as Xc = 1 / (2πfC), where f is frequency in hertz and C is capacitance in farads. It decreases as frequency increases — capacitors pass high frequencies more easily.
Inductive reactance (Xl) is the opposition an inductor presents to AC current, calculated as Xl = 2πfL, where L is inductance in henries. It increases with frequency — inductors resist high frequencies more than low ones, the opposite behavior of a capacitor.
Frequently asked questions
What's the difference between reactance and resistance?
Resistance dissipates energy as heat and is the same at all frequencies. Reactance stores and releases energy (in a capacitor's electric field or an inductor's magnetic field) and depends on frequency — it doesn't dissipate energy in an ideal component.
Why does capacitive reactance decrease with frequency while inductive reactance increases?
A capacitor charges and discharges faster at higher frequencies, offering less opposition to current flow. An inductor resists changes in current, and faster-changing (higher frequency) current meets more opposition from its magnetic field.
At what frequency are Xc and Xl equal?
That frequency is called the resonant frequency of an LC circuit, found by setting Xc = Xl and solving for f — it's an important value in filter and oscillator design, though this calculator shows both reactances separately rather than solving for resonance.