RC High-Pass Cutoff Calculator

About this calculator

An RC high-pass filter — a resistor and capacitor arranged so the output is taken across the resistor — attenuates low frequencies while letting high ones pass. Its −3 dB cutoff frequency, the point where output power drops to half (voltage to ~70.7%), is given by fc = 1 ⁄ (2πRC), where R is resistance in ohms and C is capacitance in farads.

This single-pole filter is one of the most common building blocks in analog electronics: it's used to strip DC offset and low-frequency hum from audio signals, form the “treble” stage in tone-control circuits, and AC-couple stages in amplifier and sensor circuits. Electronics designers use this calculation to pick R and C values that place the cutoff exactly where unwanted low frequencies should start being rejected.