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High Pass Filter Calculator

Calculate RC high-pass filter cutoff frequency, output voltage, gain, phase shift, or find component values for a target cutoff.

Interactive calculator

High Pass Filter Calculator

Calculate RC high-pass filter cutoff frequency, output voltage, gain, phase, or find component values.

Filter resistance

Filter capacitance

Your result will appear here.

Choose a calculation mode, fill in the known values, and click Calculate.

Quick Guide

  • Choose: cutoff frequency, output at frequency, or find R/C.
  • Enter known component values and frequency.
  • Click Calculate for gain, phase, and output voltage.

Table of Contents

Key Takeaways

  • A first-order RC high-pass filter passes high frequencies and attenuates low frequencies.
  • The cutoff frequency is fc = 1/(2πRC), where gain = −3 dB.
  • Below fc, the filter rolls off at +20 dB/decade (−6 dB/octave).
  • The output is taken across the resistor in an RC high-pass configuration.
  • Phase shift ranges from +90° (low f) to 0° (high f).

What Is a High-Pass Filter?

A high-pass filter is a circuit that allows signals with frequencies higher than a certain cutoff frequency to pass through while attenuating signals with lower frequencies. A first-order RC high-pass filter uses a capacitor in series and a resistor to ground, with the output taken across the resistor.

High Pass Filter Infographic

High-Pass Filter Formulas

fc=12πRCf_c = \frac{1}{2\pi RC}

Cutoff frequency (\u22123 dB)

VoutVin=f/fc1+(f/fc)2\frac{V_{out}}{V_{in}} = \frac{f/f_c}{\sqrt{1+(f/f_c)^2}}

Voltage gain ratio

Frequency Response

FrequencyGainPhase
0.1 fc\u221220 dB+84.3\u00B0
fc\u22123 dB+45\u00B0
10 fc\u22120.04 dB+5.7\u00B0
\u226B fc0 dB0\u00B0

How to Use

  1. 1Select a mode.
  2. 2Enter R and C for cutoff, or add frequency and voltage for output.
  3. 3Click Calculate.
  4. 4Review cutoff, gain, phase, and component values.

Example Calculations

Cutoff Frequency

R = 10 kΩ, C = 10 nF. fc = 1/(2π × 10000 × 10−8) ≈ 1.59 kHz.

Output at 500 Hz

fc = 1.59 kHz, Vin = 1 V, f = 500 Hz. Gain = 0.3 (−10.5 dB). Vout ≈ 0.3 V.

Applications

Audio bass removal, DC blocking, AC coupling between amplifier stages, removing baseline drift in sensor signals, differentiator circuits, and pre-emphasis in audio/communication systems.

Common Mistakes

  • Measuring output across the capacitor instead of the resistor.
  • Confusing high-pass and low-pass configurations.
  • Forgetting that gain at fc is −3 dB, not 0 dB.
  • Using peak voltage when RMS is needed.

Accuracy and Limitations

Assumes ideal components. Real capacitors have ESR and real resistors have parasitic capacitance. For steeper rolloff, use higher-order filters. Loading effects are not modeled.

Frequently Asked Questions

What does a high-pass filter do?›

A high-pass filter allows frequencies above its cutoff frequency to pass while attenuating lower frequencies. It blocks DC and low-frequency signals.

Where is the output measured?›

In a first-order RC high-pass filter, the output is measured across the resistor. The capacitor is in series with the signal path.

What is the rolloff rate?›

A first-order RC high-pass filter has a rolloff of +20 dB/decade (or +6 dB/octave) below the cutoff frequency.

How is this different from a low-pass filter?›

A low-pass filter passes low frequencies and attenuates high ones (output across C). A high-pass filter does the opposite (output across R). Both use the same cutoff formula.

Can I cascade high-pass filters?›

Yes, but cascading changes the overall response. Two identical first-order stages give −6 dB at fc instead of −3 dB, with a steeper rolloff.

What is the phase at the cutoff frequency?›

At fc, the phase shift is +45°. Phase ranges from +90° at very low frequencies to 0° at very high frequencies.

Sources / References

  1. All About Circuits: High-Pass Filters
  2. HyperPhysics: RC Filters
  3. NIST: SI Units
Manish Kumar

Author & technical reviewer

Manish Kumar

PhysicsCalcs tools are reviewed with an educational focus: clear formulas, transparent assumptions, and practical context for students and science learners.

Learn more about Manish