Please enter all required numeric values.
Input Parameters Specification
CapacitanceCapacitor value entered in F, µF, nF or pF.
FrequencyOperating AC frequency entered in Hz, kHz, MHz or GHz.
Capacitive ReactanceOpposition offered by the capacitor to AC signal flow.
Unit ConversionCapacitance is converted into farads and frequency into hertz before calculation.
Use CaseUseful for AC circuits, RC filters, coupling capacitors, RF networks and impedance checks.
Result UnitReactance result is shown in ohms.
Formulas & Mathematical Logic
Main formula: Xc = 1 / (2 × π × f × C). This gives capacitive reactance in ohms.
Capacitance conversion: F stays F, µF is multiplied by 0.000001, nF by 0.000000001, and pF by 0.000000000001.
Frequency conversion: Hz stays Hz, kHz is multiplied by 1000, MHz by 1000000, and GHz by 1000000000.
Practical meaning: capacitive reactance decreases as frequency or capacitance increases.
Step-by-Step Example
Example values: capacitance = 1 µF, frequency = 1 kHz.
Convert capacitance: 1 µF = 0.000001 F.
Convert frequency: 1 kHz = 1000 Hz.
Xc = 1 / (2 × π × 1000 × 0.000001).
Xc = about 159.1549 Ω.
Practical meaning: at 1 kHz, a 1 µF capacitor behaves like about 159 Ω of capacitive reactance.
About This Calculator
Find how much a capacitor resists AC signal flow at any frequency.
This CalcBoy calculator converts capacitance and frequency into capacitive reactance, also called capacitor impedance magnitude.
The Capacitor Impedance Calculator is useful for AC circuit design, RC filters, coupling capacitors, bypass capacitors, audio circuits, RF networks and power electronics. In DC steady state, an ideal capacitor blocks current. In AC circuits, it allows current to flow depending on frequency and capacitance. This opposition to AC is called capacitive reactance.
Best UseRC filters, audio coupling, AC analysis, RF circuits and impedance checks.
Key InputsCapacitance and frequency with practical unit selectors.
Design BenefitQuickly check whether a capacitor is high or low impedance at a target frequency.
Practical ReminderReal capacitors also have ESR, ESL, leakage and self-resonant frequency.
Capacitive reactance is inversely proportional to both frequency and capacitance. A larger capacitor gives lower reactance at the same frequency. A higher frequency also lowers reactance. This is why capacitors are often used for AC coupling, high-frequency bypassing, and filtering.
Quick tip: for bypass work, choose a capacitor whose reactance is low at the unwanted noise frequency, but also check ESR and self-resonance.
Real capacitor impedance is not only Xc. At high frequency, equivalent series resistance and inductance can dominate. Ceramic, film, electrolytic and RF capacitors behave differently, so use this calculator for the ideal reactance estimate, then confirm final performance with datasheet impedance curves when accuracy matters.
Frequently Asked Questions
What is capacitive reactance?
Capacitive reactance is the opposition a capacitor gives to AC current, measured in ohms.
Does capacitor impedance decrease with frequency?
Yes. Ideal capacitive reactance decreases when frequency increases.
What is the formula for capacitor impedance?
For ideal capacitive reactance magnitude, Xc = 1 / (2 × π × f × C).
Can I use this for RF circuits?
Yes, for ideal reactance estimates. RF designs should also consider ESR, ESL and self-resonant frequency.
Why is DC blocked by a capacitor?
At zero frequency, ideal capacitive reactance becomes extremely high, so DC steady-state current is blocked.
What units does this calculator use?
It converts capacitance into farads and frequency into hertz, then outputs reactance in ohms.