📡 Pi Attenuator Calculator
Calculate the resistor values for a matched resistive Pi (π) attenuator from your target attenuation and system impedance.
What this calculator does
A resistive Pi (π) attenuator reduces signal power by a set amount in dB while staying matched to a given system impedance (commonly 50Ω for RF work), using three resistors arranged in a π shape: two shunt resistors to ground and one series resistor.
The formulas
Given a voltage ratio K = 10^(dB/20), the standard matched-Pi formulas are: series resistor R2 = Z0 × (K² − 1) / (2K), and shunt resistors R1 = R3 = Z0 × (K + 1) / (K − 1).
These are ideal resistor values assuming perfect components; real builds should use the closest standard resistor values available and verify return loss, since small mismatches affect impedance matching more at very low or very high attenuation settings.