Enter the two resistances R1 and R2 and the two capacitances C1 and C2 into the calculator to determine the cutoff frequency of the bandpass filter.

## Bandpasss Filter Formula

The following formula is used to calculate the cutoff frequencies of a bandpass filter.

LCF = 1/2*pi*R2*C2

HCF = 1/2*pi*R1*C1

• Where LCF is the lower cutoff frequency (hz)
• HCG is the high cutoff frequency (hz)
• R1 and R2 are the resitances in a passive bandpass filter
• C1 and C2 are the capacitances in a passive bandpass filter

## Example Problem

How to calculate the cutoff frequencies of a bandpass filter?

First, deter the resistance and capacitance of C1 and R1. These should be as depicted below in the circuit.

For this example, the first capacitances and resistances are 10 farads and 4 ohms respectively. Keep in mind these may not be realistic for real-world bandpass filters but can be used to show the calculations more simply.

Next, determine the second capacitance and resistance. In this case, these values are found to the 5 farads and 2 ohms respectively.

Finally, calculate the lower and upper cutoff frequencies.

LCF = 1/2*pi*R2*C2

= 1/(2*3.14159*5*2)

= .0159 hz

HCF = 1/2*pi*R1*C1

= 1/(2*3.14159*10*4)

= .00397 hz.