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High-Pass Filter Calculator.

Calculate the ideal first-order passive RC high-pass cutoff and gain magnitude.

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01

Set your values

Results update as you type.

Cutoff frequency: 1,591.549431 Hz

Cutoff frequency

0.000000Hz
Gain magnitude: 0.782479 ×

Gain magnitude

0.000000×
Gain (dB): -2.130546 dB

Gain (dB)

0.000000dB

Results update automatically as you type.

Educational idealized model with every parameter shown; this tool does not size wiring, components, or safety systems.

Use Cases

Design audio crossover networks

Determine the cutoff frequency and gain response to select appropriate RC values for separating high and low frequencies in speaker systems.

Example: Set R=8 Ω and C=10 µF to get a cutoff around 2 kHz for a tweeter.

Analyze signal conditioning circuits

Evaluate how a high-pass filter attenuates low-frequency noise or DC offset while passing higher-frequency signals of interest.

Example: Check gain at 1 kHz with R=1 kΩ and C=0.1 µF to see if the signal is passed adequately.

Frequently Asked Questions

What does this high-pass filter calculator do?
This calculator determines the cutoff frequency (where output is -3 dB) and the gain magnitude at a given frequency for a first-order passive RC high-pass filter. You input resistance (Ω), capacitance (F), and frequency (Hz).
How is the cutoff frequency calculated?
The cutoff frequency (fc) is calculated using the formula fc = 1 / (2πRC), where R is resistance in ohms and C is capacitance in farads. At this frequency, the output amplitude is 70.7% of the input, corresponding to -3 dB.
What is the gain magnitude at a specific frequency?
The gain magnitude is the ratio of output voltage to input voltage at the given frequency. It is calculated as f / sqrt(f^2 + fc^2) for a high-pass filter, where f is the frequency and fc is the cutoff frequency. It ranges from 0 at DC to 1 at high frequencies.

Tips & Common Mistakes

Tips

  • Ensure resistance is in ohms (Ω) and capacitance in farads (F). For small capacitors, convert µF to F (1 µF = 1e-6 F).
  • The cutoff frequency is where the gain magnitude is 0.707 (or -3 dB). Use this as a reference for filter bandwidth.
  • For frequencies much higher than cutoff, the gain approaches 1 (0 dB). For frequencies much lower, gain drops linearly with frequency.
  • Double-check your units: if you use kΩ and µF, the cutoff frequency will be in kHz, but the calculator expects base units.

Common Mistakes to Avoid

  • Forgetting to convert capacitance from µF to F, leading to cutoff frequency off by a factor of 1e6.
  • Using the formula for a low-pass filter instead of high-pass, which would give incorrect gain magnitude.
  • Assuming the gain magnitude is in dB; the calculator provides a linear ratio, not decibels.

Last updated: August 13, 2026