RC and RLC filter calculator
A free RC and RLC filter calculator. Enter the component values and get the cutoff frequency, time constant, resonant frequency, quality factor Q, and damping ratio, then jump to the full Bode plot.
Cutoff and resonant frequency
For a first-order RC filter the cutoff frequency is f_c = 1/(2πRC). For a series RLC circuit the resonant frequency is f₀ = 1/(2π√(LC)), and the quality factor Q = (1/R)·√(L/C) sets how sharp the resonance is. The magnitude and phase response are plotted right below the numbers.
Frequently asked questions
- How do you calculate the cutoff frequency of an RC filter?
- The −3 dB cutoff frequency of a first-order RC filter is f_c = 1/(2πRC), with time constant τ = RC. This calculator computes it from your resistor and capacitor values and plots the magnitude and phase response.
- What is the resonant frequency of an RLC circuit?
- For a series RLC circuit the resonant frequency is f₀ = 1/(2π√(LC)). The quality factor Q = (1/R)·√(L/C) sets how sharp the resonance is, and the damping ratio is ζ = 1/(2Q).
- What is the difference between a low-pass and a high-pass filter?
- A low-pass filter passes frequencies below its cutoff and attenuates higher ones; a high-pass filter does the opposite. An RC low-pass takes its output across the capacitor, while a high-pass takes it across the resistor.
- Is this RC/RLC filter calculator free?
- Yes, it is free and entirely browser-based.