📶 Cutoff Frequency Calculator
Calculate the cutoff frequency of a simple RC filter circuit, the point where output signal power drops to half.
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µF
What the cutoff frequency is
In an RC filter circuit, the cutoff frequency marks the point where the output signal’s power drops to half its passband value (about a 3 dB drop), separating the frequencies that pass through from those that are attenuated.
The formula
For a simple first-order RC filter (low-pass or high-pass), the cutoff frequency is fc = 1 / (2πRC), where R is resistance in ohms and C is capacitance in farads. The same formula applies to both low-pass and high-pass RC filter topologies.
This calculator is for general electronics education and filter design reference.
Last reviewed August 2026