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Cutoff Frequency Calculator.

Calculate the −3 dB cutoff frequency of a first-order RC filter.

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cutoffFrequency: 15.915494 Hz

cutoffFrequency

0.000000Hz

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This page applies only the stated idealized equation and explicit inputs; verify specialized engineering, medical, or safety decisions against applicable standards.

Use Cases

Designing audio filters

Determine the cutoff frequency for a simple RC low-pass or high-pass filter in audio circuits to set the frequency range for treble or bass control.

Example: For R=1kΩ and C=100nF, fc ≈ 1.59 kHz.

Signal conditioning in sensors

Set the cutoff frequency to filter out noise or unwanted high-frequency components from sensor signals before further processing.

Example: Choose R and C to achieve a desired fc for a temperature sensor output.

Frequently Asked Questions

What is the cutoff frequency of an RC filter?
The cutoff frequency (fc) is the frequency at which the output power drops to half its mid-band value, corresponding to a -3 dB point. For a first-order RC filter, it is calculated as fc = 1/(2πRC).
How do I use this calculator?
Enter the resistance in ohms (Ω) and capacitance in farads (F). The calculator will compute the -3 dB cutoff frequency using the formula fc = 1/(2πRC). Ensure units are consistent (e.g., use ohms and farads).
What are typical applications of cutoff frequency?
Cutoff frequency is used in designing low-pass and high-pass filters, audio crossover networks, and signal conditioning circuits. It defines the frequency range where the filter passes signals with minimal attenuation.

Tips & Common Mistakes

Tips

  • Use consistent units: if resistance is in ohms and capacitance in farads, the result will be in hertz.
  • For quick estimates, remember that fc ≈ 0.159/(RC) when R is in ohms and C in farads.
  • Check your component values: typical capacitors are in microfarads (µF) or nanofarads (nF), so convert to farads before calculating.
  • The formula assumes an ideal first-order RC filter; real components may have parasitic effects.

Common Mistakes to Avoid

  • Forgetting to convert capacitance from µF or nF to farads, leading to incorrect results.
  • Using the formula for a second-order filter or other configurations, which have different cutoff frequency expressions.
  • Assuming the cutoff frequency is the same for low-pass and high-pass filters; it is, but the circuit configuration matters for the response.

Last updated: August 13, 2026