So, I was surfing the web and didn't find what I was looking for so I created it, lol...

I was looking for a quick calculator to tell me if that supercharger I was looking at would work for my application. I wanted to be sure I chose the correct pulley size without over spinning the supercharger, then once I started playing with the math I figuresd others may want this info too.

Calculate Supercharger Shaft Speed
Enter the crank pulley diameter and super pulley diameter to just get the Rotation Ratio (How many times the SC shaft pins per crankshaft rotation), adding the engine RPM will get you the superchargers shaft speed at that engine RPM
Crank Pulley Diameter
SC Pulley Diameter
Rotation Ratio
Engine RPM - Optional
SC Shaft Speed at given engine RPM

Calculate SC Pulley size
Enter the crank pulley diameter and SC Shaft Speed at disired Engine RPM, adding Estimated Efficiency can help you figure out the smallest pulley at the Max SC Shaft Speed and Max Engine RPM, but can help tune the pulley size for efficiency in the lower RPM's as well,
Example --> What is the smallest pulley I can run for Max Efficiency if the Max SC Shaft speed is 13000 RPM and the max Engine RPM is 6500 on a 8.5" Crank pulley, knowing that the SC is only 96% efficient?
Or --> I want to know what pulley size to run if I want 4000 RPM SC Shaft Speed @ 2000 Engine RPM with a 9" Crank pulley?
Crank Pulley Diameter
Engine RPM
SC Shaft Speed
Estimated Efficiency Percentage Enter 95 for 95% - Optional
SC Pulley Diameter