Capacitive Reactance Calculator
Enter a frequency and a capacitance to find the capacitive reactance Xc in ohms. Reactance is the opposition a capacitor presents to alternating current, and it falls as either the frequency or the capacitance rises.
How to use the capacitive reactance calculator
- Enter the signal frequency in hertz (or kilohertz).
- Enter the capacitance in farads (or microfarads, nanofarads).
- Read the capacitive reactance Xc in ohms.
Examples
1 microfarad at 1 kHz
f = 1000 Hz, C = 1e-6 F
Xc = 159.15 ohm
10 microfarads at mains 60 Hz
f = 60 Hz, C = 1e-5 F
Xc = 265.26 ohm
Frequently asked questions
What is capacitive reactance?
Capacitive reactance Xc is the opposition a capacitor offers to alternating current, measured in ohms. It is given by Xc = 1 / (2 pi f C).
Why does reactance fall as frequency rises?
Frequency sits in the denominator, so doubling the frequency halves the reactance. At high frequencies a capacitor behaves more like a short circuit.
What is the reactance of a 1 microfarad capacitor at 1 kHz?
About 159.15 ohms, from Xc = 1 / (2 pi * 1000 * 1e-6).
Is reactance the same as resistance?
No. Both are measured in ohms, but reactance applies to alternating current and shifts the phase between voltage and current by 90 degrees, while resistance does not.
How do I find total impedance?
For a pure capacitor the impedance magnitude equals the reactance. With series resistance R, combine them as the square root of R squared plus Xc squared.
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