RF Attenuator Calculator: T-Pad and Pi-Pad Resistor Values with Power Rating

Formulas use the standard matched-pad equations referenced to the voltage attenuation ratio K = 10^(dB/20). Power dissipation assumes a perfectly matched source and load at Z0. Real builds should add margin for tolerance and mismatch — we recommend at least 2× headroom over the calculated worst-case resistor power above. The Pi-pad kit is designed for 1206 footprint resistors (commonly rated around 0.25 W) with 0805 also supported (commonly rated around 0.125 W); if your calculated dissipation exceeds these ratings even with margin, consider a higher-power resistor series or our fixed coaxial attenuator instead.