Cutoff Frequency Calculator: RC, RL, and LC Filters

Your details

RC and RL are 1st-order filters. LC is a 2nd-order resonant circuit.
Choose which quantity to solve for. The others become inputs.
Resistance in the selected unit.
Capacitance in the selected unit.
Enter the desired cutoff frequency in hertz to solve for a component value.
Hz
Cutoff frequency (-3 dB)
636.620 Hz

The frequency at which the output power falls to half (-3 dB) of the passband level.

Time constant (tau)250.0000 us
Reactance at fc10000.00 ohm
Cutoff frequency (Hz)636.6197723675813
Angular frequency (rad/s)3999.9999999999995

Cutoff frequency: 636.620 Hz

  • At 636.620 Hz, output power is exactly half (-3 dB) of the passband value, and output voltage is 0.707 (about 70.7%) of the input.
  • The time constant is 250.0000 us: a step input takes about 5 time constants (1.250 ms) to settle within 1% of its final value.
  • This is a first-order filter: the Bode magnitude plot rolls off at -20 dB per decade (6 dB per octave) beyond the cutoff.

Next stepUse the Bode plot below to see how gain varies with frequency from 0.01 fc to 100 fc.

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