What is a high-pass filter?

A high-pass filter (HPF) is a circuit that allows signals with a frequency higher than a specified cutoff frequency to pass through while attenuating signals below that frequency.

What is the cutoff frequency formula for an RC high-pass filter?

The cutoff frequency is fc = 1 / (2π × R × C), where R is in ohms and C is in farads. At this frequency, the output is -3 dB (about 70.7%) of the input.

What is the cutoff frequency formula for an RL high-pass filter?

For an RL filter, fc = R / (2π × L), where R is in ohms and L is in henries.

What does -3 dB mean?

The -3 dB point is where the output power drops to half of the input power, or equivalently, the output voltage is about 70.7% of the input voltage. It marks the effective cutoff of the filter.

Can I solve for R, C, or L from a target frequency?

No. This calculator requires both component values and computes the resulting cutoff frequency. To reverse-solve, rearrange the displayed cutoff formula for the component you need.

What is phase shift at the cutoff frequency?

At the -3 dB cutoff frequency, an RC or RL high-pass filter introduces a +45° phase shift on the output relative to the input.

High Pass Filter Calculator

Calculate cutoff frequency, gain, and phase for an RC or RL high-pass filter from its component values.

Filter Configuration

Filter Type

RC Filter RL Filter

Resistance (R)

Capacitance (C)

Signal Frequency (optional) — for gain & phase

Results

Enter component values and click Calculate

Summary

Calculate cutoff frequency, gain, and phase for an RC or RL high-pass filter from its component values.

How it works

Select the filter type: RC (resistor-capacitor) or RL (resistor-inductor).
Enter the known component values — resistance (R) and capacitance (C) for RC, or resistance (R) and inductance (L) for RL.
Optionally enter a signal frequency to compute the gain and phase shift at that point.
Click Calculate to get the cutoff frequency (fc), reactance, and attenuation.
Use the results to verify or select components for your filter circuit.

Use cases

Design audio high-pass filters to remove low-frequency hum or rumble.
Verify component values for signal-conditioning circuits.
Compute cutoff frequency for power supply noise filters.
Evaluate how changing inductance or capacitance moves the cutoff frequency.
Analyze phase shift introduced by a filter at a given frequency.
Teach or learn passive filter theory with instant feedback.

Frequently Asked Questions

Last updated: 2026-09-22 · Reviewed by Nham Vu