RC Filter Calculator

Your details

Low-pass: attenuates frequencies above the cutoff. High-pass: attenuates frequencies below the cutoff.
Choose the unknown to calculate. The other two fields are your inputs.
The series resistance of the RC filter.
kOhm
The capacitance of the RC filter.
uF
The desired -3 dB cutoff frequency used when solving for R or C.
Hz
The frequency of your input signal. Gives gain, attenuation in dB, and phase shift at that frequency.
Hz
Cutoff frequency (fc)
15.9155 Hz

The -3 dB point: output voltage is 0.7071 of input, output power is halved.

Time constant (tau = RC)10.0000 ms
Capacitive reactance (Xc) at fc10.000 kΩ
Total impedance (|Z|) at fc14.142 kΩ
Gain at cutoff0.7071 (-3.01 dB)
Phase shift at cutoff-45 deg
Gain at signal frequency0.7071 (-3.01 dB)
Phase shift at signal freq-45.00 deg
fc Hz15.915494
Gain dB signal-3.01
Phase deg signal-44.999
R ohms10,000
C farads0.000001

Low-pass RC filter - cutoff at 15.9155 Hz

  • At the cutoff frequency (15.9155 Hz), the output voltage drops to 0.7071 of the input (-3.01 dB). Output power is halved.
  • This low-pass filter passes signals below 15.9155 Hz with minimal loss. Above the cutoff, attenuation increases at -20 dB per decade (-6 dB per octave).
  • At your signal frequency (15.9150 Hz), below the cutoff, the gain is -3.01 dB.

Next stepTo cascade two identical stages for a -40 dB/decade roll-off, the combined -3 dB point shifts to approximately fc x 0.644. Adjust fc accordingly.

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