This calculates capacitor impedance given the capacitance value and the frequency





Our capacitance impedance calculator helps you calculate the impedance of a capacitor if its capacitance value C and frequency f of the signal passing through it is given. You can select capacitance units in microfarads, farads, nanofarads and picofarads. The frequency input should be in hertz. 



$$X_{C} = \frac{1}{\omega C} = \frac{1}{2 \pi fC}$$


$$X_{C}$$ = capacitor impedance in ohms (Ω)

$$\omega$$ = radian frequency in rad/s = $$2 \pi fC$$ where $$f$$ is the frequency in hertz.

$$C$$ = capacitance in farads (F).

Impedance is the property of a material to resist alternating current. It is analogous to resistance; in fact, the impedance of a resistor is simply its resistance. The impedance of a capacitor is also called its capacitive reactance

Based on the formula above, it can be said that impedance is a function of both the value of the capacitance and frequency of the signal involved. The higher the frequency, the lower the impedance of the capacitor and vice versa. This is why capacitors act as a short circuit (very low impedance) for higher frequency signals and an open circuit (very high impedance) to lower frequency signals. 

Coupling capacitors employs the theory of capacitive impedance. A coupling capacitor connects or "couples" two stages of amplifiers. In an amplifier, both DC and AC signals are present. The capacitor acts as an open circuit to DC signals (zero frequency) so that it may not reach the next stage. 

Further Reading

Textbook - AC Capacitor Circuits

Textbook - Series Resistor-Capacitor Circuits

Worksheet - Capacitive Reactance



  • WA7PRC 2016-09-02

    Since it calculates only Xc (which is NOT impedance), this is not a very useful tool. Who DOESN’T recall the formula for Xc?

    Frequency can be entered in ONLY Hertz, making this tool not very user-friendly above audio frequencies. Those of us working into the GHz region would have to enter LOTS of zeros.

  • Richard Nelson 2016-09-03

    Many of the “calculators” here are just simple formula solvers.  That is not very flexible.  What should be used is an equation solver wherein all the variable values that are known are input and the solver provides the unknown value.  My simple HP calculator does that.  AND, just like WA7PRC says, the input units are inconveniently limited.  Use the computer for what it can do.  X < > Y,  Richard