Solve for Reactance, Frequency, or Capacitance
The page uses a single stacked layout, while the input controls adapt to 3 columns on large screens, 2 on smaller screens, and 1 on mobile.
Reactance vs Frequency Curve
The chart updates from your solved frequency and capacitance values. It highlights the operating point on the curve.
Physics Behind the Calculator
Capacitive reactance is the opposition a capacitor offers to alternating current. It depends on both signal frequency and capacitance.
Xc = 1 / (2πfC)Where:
- Xc = capacitive reactance in ohms
- f = frequency in hertz
- C = capacitance in farads
When voltage is supplied, the calculator estimates RMS current for an ideal capacitor. It also shows the impedance as -jXc, which represents a 90 degree lead of current relative to voltage in an ideal capacitive circuit.
Steps for Accurate Input
- Select whether you want to solve for reactance, frequency, or capacitance.
- Enter the known values in the visible fields.
- Pick the correct units for each value.
- Optionally enter voltage to estimate current and reactive power.
- Click Calculate to show the result above the form.
- Review the graph, interpretation, and downloadable report files.
Sample Capacitor Reactance Values
| Frequency | Capacitance | Reactance |
|---|---|---|
| 50 Hz | 100 µF | 31.831 Ω |
| 60 Hz | 47 µF | 56.441 Ω |
| 1 kHz | 10 µF | 15.915 Ω |
| 10 kHz | 220 nF | 72.343 Ω |
| 100 kHz | 1 nF | 1.592 kΩ |
These examples help verify your own calculation results and show how reactance drops as either frequency or capacitance increases.
Common Questions
1) What does capacitor reactance mean?
It is the opposition a capacitor gives to alternating current. Unlike resistance, reactance changes with frequency. Higher frequency usually means lower capacitive reactance.
2) Why does reactance decrease when frequency increases?
The formula places frequency in the denominator. As frequency rises, the capacitor charges and discharges more often, so it opposes AC less strongly.
3) Which unit should I use for capacitance?
Use the unit that matches your component marking. Small capacitors are often in nF or pF, while larger electrolytic capacitors are commonly listed in µF.
4) Can this tool solve for frequency too?
Yes. Change the mode to frequency, enter reactance and capacitance, then submit. The calculator rearranges the same core equation automatically.
5) Is this valid for DC circuits?
No. Capacitive reactance describes AC behavior. In steady DC conditions, an ideal capacitor behaves like an open circuit after charging.
6) Why is impedance shown as -jXc?
The minus imaginary term represents phase behavior. In an ideal capacitor, current leads voltage by 90 degrees, so impedance is purely negative imaginary.
7) What happens if I enter voltage?
The calculator estimates RMS current using I = V / Xc. It also reports reactive power magnitude for the ideal capacitor case.
8) Are the results exact for real components?
They are ideal-theory values. Real capacitors have tolerance, leakage, equivalent series resistance, and parasitic inductance that can affect actual performance.