Why have a calculator when we have MBR to just ask? Follow the path of least resistance is my motto!What does yours do that this one doesn't?
The program can be downloaded from http://jimsitton.net/ratiocalc/
The program allows for up to three ratios in series.
If you have fewer just leave the unused ratios set to 1:1.
The program will also calculate speed based on engine RPM, drive ratio,and wheel diameter.
Be sure to measure the outside diameter of your wheel for accurate results.