Pi Pad Attenuator Calculator

A Pi Pad attenuator is one in which the resistors are in a π configuration. The shunt resistors (R1) are connected to ground, while the series resistor (R2) is connected between them.

This forms a Pi Network.

Enter the desired value of attenuation and the characteristic impedance (default value is 50 ohm).


R1 = Zo [10dB/20 + 1] / [10dB/20 – 1]

R2 = Zo/2 [10dB/10 – 1] / [10dB/20]

where R1 is the shunt resistor and R2 is the series resistor. To build this attenuator you will need

  • two shunt resistors – one at the input and the other at the output
  • one series resistor

Note that it is assumed that both the source and load resistance are equal in this calculation.


[1] Pi Pad Attenuator on Wikipedia