Capacitor Frequency Calculator

This tool calculates the cut-off frequency of a capacitor, within the context of a circuit, such as in an RC (resistor-capacitor) filter.





fc​ = 1/(2π*R*C)​

  • fc​ is the cutoff frequency in Hertz (Hz)
  • R is the resistance in Ohms (Ω)
  • C is the capacitance in Farads (F)
  • π is the mathematical constant Pi (approximately 3.14159)

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Example Calculation

The cutoff frequency for a RC network with R = 10 kΩ and C = 1 nF is 15.92 kHz. For a low pass filter, signals at frequencies above this value will be attenuated. For a high pass filter, signal frequencies below this value will be attenuated.

A schematic drawing of a simple low pass filter is shown below

RC low pass Filter Schematic

And here is the frequency response

Butterworth response

The calculator to find the 3 dB point shown above for R and C values.


One of the most fundamental characteristics to calculate is the cutoff frequency (fc) of an RC filter. This is the frequency value at which the output signal drops to 70.7% (or -3 dB) of its input signal level for a low-pass or high-pass filter.

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