Capacitive Reactance Calculator
Find the reactance of a capacitor at a given frequency. Enter the frequency (Hz, kHz or MHz) and the capacitance (pF, nF, µF, mF or F) to get the capacitive reactance Xc in ohms.
Example: with Frequency 60 · Frequency unit Hz · Capacitance 10 · Capacitance unit µF → Capacitive reactance: 265.2582 Ω.
- Reactance in ohms265.2582 Ω (exact)
- How it behavesReactance falls as frequency or capacitance rises; at DC (0 Hz) a capacitor blocks current entirely.
Computed by the calculator below using its default values. Change any input to see your own numbers.
Capacitive reactance Xc = 1/(2πfC). It falls as frequency or capacitance rises, so a capacitor blocks low frequencies (and DC) but passes high ones.
Why a capacitor's opposition depends on frequency
A capacitor stores charge, and it takes time to charge and discharge. At low frequencies the voltage changes slowly, the capacitor keeps up and largely blocks the current, so its reactance is high. At high frequencies the voltage reverses before much charge builds, current flows more freely, and the reactance is low. The relationship is Xc = 1/(2πfC): reactance is inversely proportional to both frequency and capacitance.
This frequency dependence is what makes capacitors useful as filters. A coupling capacitor passes an audio or radio signal while blocking the DC bias behind it; a bypass capacitor shunts high-frequency noise to ground while ignoring the slow supply voltage. Unlike a resistor, a capacitor's reactance dissipates no power — the current and voltage stay 90 degrees out of phase.
How it’s calculated
Capacitive reactance Xc = 1/(2πfC), with frequency f in hertz and capacitance C in farads. Inputs convert with kHz = 1e3 Hz, MHz = 1e6 Hz, mF = 1e-3 F, µF = 1e-6 F, nF = 1e-9 F, pF = 1e-12 F. Reactance is reported in ohms.
An ideal capacitor with no equivalent series resistance or leakage. Real capacitors deviate at very high frequencies where parasitic inductance takes over.
Capacitive reactance at 60 Hz
| Capacitance | Reactance Xc |
|---|---|
| 1 µF | 2,653 Ω |
| 10 µF | 265.3 Ω |
| 100 µF | 26.5 Ω |
| 1,000 µF | 2.65 Ω |
Computed with Xc = 1/(2π·60·C); rounded.
Common mistakes
- Dropping the 2π factor, which overstates the reactance by more than six times.
- Forgetting to convert prefixes — a µF is 10⁻⁶ F and a pF is 10⁻¹² F.
- Treating reactance like resistance and adding it to a resistor arithmetically; they combine as vectors 90° apart.
- Expecting a capacitor to pass DC — at 0 Hz the reactance is infinite.
Frequently asked questions
What is the capacitive reactance formula?
Xc = 1/(2πfC), where f is the frequency in hertz and C is the capacitance in farads. The reactance comes out in ohms.
Why does reactance drop as frequency rises?
At higher frequencies the voltage reverses before the capacitor fully charges, so more current flows. Since Xc is inversely proportional to frequency, doubling the frequency halves the reactance.
What is a capacitor's reactance at DC?
Infinite. At 0 Hz the formula divides by zero, which matches reality: a fully charged capacitor blocks steady direct current.
Is reactance the same as resistance?
No. Both are measured in ohms, but reactance stores and returns energy rather than dissipating it, and it shifts current 90 degrees out of phase with voltage.