Low Pass Filter Calculator

Your details

Choose the circuit topology. RC and RL are first-order passive; LC is second-order passive; op-amp types are active first-order.
Series resistance in ohms. Leave blank to solve for R from the cutoff frequency and the other component.
ohm
Capacitance in farads. 159 nF = 0.000000159 F. Leave blank to solve for C.
F
The frequency of the input signal. Used to compute how much the filter attenuates and phase-shifts that specific frequency.
Hz
Cutoff frequency (-3 dB)Passband (low attenuation)
1,000.9745Hz

The frequency at which output power drops to half (-3 dB).

Cutoff (auto-scaled)1.001 kHz
Time constant159.0 us
DC gain1
Gain at signal frequency0.8946
Attenuation at signal frequency-0.97dB
Phase shift at signal frequency-26.54deg
Filter order1st order (-20 dB/decade)
-0.97 dB
Stopband<-20Transition-20--3Passband-3+

Cutoff frequency: 1.001 kHz

  • The -3 dB cutoff is 1.001 kHz. Signals well below this frequency pass through almost unchanged; signals well above it are progressively attenuated.
  • The time constant is 159.0 us, which is how long the circuit takes to charge to about 63% of a step input.
  • Your signal at 500.0 Hz is below the cutoff (in the passband). At this frequency the filter provides -0.97 dB of attenuation.

Next stepFor sharper roll-off, consider cascading two first-order sections or switching to an LC design.

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