Capacitive Reactance Calculator
Capacitive Reactance (XC)2,652.5824 Ω
The Capacitive Reactance Calculator shows how much a capacitor resists alternating current at a chosen frequency. Unlike an inductor, a capacitor presents less opposition as frequency climbs, which is what lets it block DC while passing AC and high-frequency signals. Enter the frequency and capacitance, choose units, and read XC in ohms.
Formula
XC = 1 / (2·π·f·C)
- XC
- Capacitive reactance in ohms
- f
- Frequency of the AC signal in hertz
- C
- Capacitance in farads
How it works
- Enter the AC frequency (Hz, kHz, or MHz) and the capacitance (from farads down to picofarads).
- The calculator converts everything to base units and evaluates XC = 1 / (2·π·f·C).
- Because XC is inversely proportional to both frequency and capacitance, doubling either one halves the reactance.
Worked example
A 1 µF capacitor in a 60 Hz mains circuit.
- Convert: C = 1 µF = 0.000001 F.
- Denominator = 2 × π × 60 × 0.000001 = 0.000376991.
- XC = 1 / 0.000376991 ≈ 2652.5824 Ω.
The reactance is about 2652.5824 Ω.
Frequently asked questions
- Why does capacitive reactance fall as frequency rises?
- A capacitor charges and discharges faster at higher frequencies, so more current flows for the same voltage. That increased current for a fixed voltage means a lower effective opposition, or reactance.
- What happens to reactance at DC?
- At zero frequency the reactance is infinite, so an ideal capacitor blocks DC completely. This calculator needs a positive frequency because the formula divides by f.
- How does XC relate to impedance in an RC circuit?
- In a series RC circuit the impedance magnitude is the square root of (R squared plus XC squared), and the current leads the voltage. The value from this tool is the XC term in that expression.