🔻 Low Pass Filter Calculator
Enter the resistor and capacitor values of your RC low pass filter to find its cutoff (-3dB) frequency.
What This Calculator Does
A resistor-capacitor (RC) low pass filter lets low-frequency signals pass through while attenuating higher frequencies above its cutoff point. This calculator finds the cutoff frequency, angular frequency, and time constant of a simple first-order RC low pass filter from its component values.
The Formula
The cutoff (-3dB) frequency is fc = 1 ÷ (2πRC), where R is resistance in ohms and C is capacitance in farads. At this frequency, the output signal amplitude has dropped to about 70.7% of the input (a 3dB reduction in power), and it falls off further at roughly 20dB per decade above that point.
- Time constant (τ = RC): the time it takes the output to reach about 63% of a step-input change.
- Angular frequency (ω = 2πfc): the cutoff expressed in radians per second, often used in transfer-function math.
This is the standard first-order filter model used in general electronics design and education; real circuits may show slightly different behavior due to component tolerances and load impedance.