Pick your Filter Type (RC, RL, or LC), choose what you want to Solve for, then enter your Resistance (R), Capacitance (C), and/or Inductance (L) values with their units to calculate the Cutoff Frequency — plus the Time Constant (τ) and Angular Frequency (ω) as a bonus.
Cutoff Frequency
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Time Constant (τ)
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Angular Frequency (ω)
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Cutoff frequency (also called corner frequency or break frequency) is the frequency at which the output power of a filter circuit drops to half of its maximum value, or equivalently, where the voltage gain drops by 3dB (to 1/√2 of maximum).
The -3dB point represents where the output power drops to 50% of the input power. This is a standard reference point because it represents the half-power frequency, making it a meaningful measure of filter performance.
For an RC filter, the cutoff frequency is calculated using the formula: fc = 1/(2πRC), where R is resistance in ohms and C is capacitance in farads. This applies to both low-pass and high-pass RC filters.
RC filters use resistors and capacitors, RL filters use resistors and inductors, and LC filters use inductors and capacitors. RC and RL filters have gradual roll-off characteristics, while LC filters can have sharper frequency responses.
For an RL filter, use the formula: fc = R/(2πL), where R is resistance in ohms and L is inductance in henries. RL high-pass filters pass high frequencies, while RL low-pass filters pass low frequencies.
The time constant (τ) is the time it takes for a circuit's response to reach 63.2% of its final value. For RC circuits: τ = RC, for RL circuits: τ = L/R. The cutoff frequency is related by fc = 1/(2πτ).
Yes, this calculator works for both low-pass and high-pass filters. The cutoff frequency formula is the same regardless of filter type - only the circuit configuration (component arrangement) differs between low-pass and high-pass designs.