Capacitive Reactance (Xc)

Enter frequency and capacitance to calculate reactance instantly. Includes unit conversions and Show Work.

How to Use

  1. Enter a frequency (Hz / kHz / MHz).
  2. Enter a capacitance value (pF / nF / µF / mF / F).
  3. View Xc instantly in ohms (Ω). Turn on auto-scale for kΩ/MΩ.
  4. Open “Show Work” to see the formula and steps in base units.
AC Capacitor View
Xc decreases as frequency or capacitance increases.
f
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C
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Xc
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AC signal Capacitor (C) Reactance: Xc Formula: Xc = 1 / (2π f C)
Inputs & Settings
Enter frequency and capacitance. Results update instantly.
Common: 50/60 Hz mains, 1 kHz audio, 100 kHz–10 MHz switching/RF
Examples: 100 pF RF, 100 nF decoupling, 10–470 µF electrolytic
Show Work (step-by-step)
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Work is shown in base units: Hz and farads (F), with Xc in ohms (Ω).

Capacitive Reactance Formulas

Quick answer: Capacitive reactance is the AC “resistance” of a capacitor: Xc = 1 / (2π f C).

As frequency increases or capacitance increases, Xc decreases.

  • Xc (Ω): Xc = 1 / (2π f C)
  • f (Hz): frequency in hertz
  • C (F): capacitance in farads
  • π: pi ≈ 3.14159
Note: Xc is a magnitude. In impedance form, a capacitor is Zc = −jXc.

FAQ

Why does Xc go down when frequency goes up?

Because a capacitor allows more AC current to pass as the signal changes faster. The formula has f in the denominator.

Is Xc the same as resistance?

Not exactly. Resistance dissipates power as heat. Reactance stores and releases energy, and shifts phase.

What happens at DC (0 Hz)?

At ideal DC, f = 0, so Xc → ∞ (open circuit). Real capacitors leak and have ESR.

What is ESR and does this tool include it?

ESR is equivalent series resistance. This calculator computes ideal reactance only; ESR/ESL are not included.

Tool Info

Last updated:

Updates may include UI improvements, expanded unit support, and calculation edge-case handling.