I made this spreadsheet several years ago when I was calculating my RPM difference for a 4.56 gear swap in my Ram. It has grown immensely over the years with the addition of the 66/68RFE 6 speed (The real 6 speed) in the Cummins and the 2012 2500 Hemi Ram, the renamed 545RFE to 65RFE, and now the 8HP70 that I just added this morning. You can change the tire sizes, gear ratio, and the speed on the top gear section and the rest automatically populates. The rest of the sheet is locked to prevent changes, but you can easily unlock it if needed, password is blank.
There's also a tire size calculator that allows you to compare different sizes and see what the speedometer difference will be. You can change the default speed on the factory tire size line, this will be the actual speed the vehicle is traveling and the cells below is what the speedo will show. For instance, you jump from a 265/50/20 to 285/50/20 and when you're going 70, the speedo will show about 68. It also shows your effective gear ratio compared to stock with different size tires.
There is also simple MPG calculator. This can be used to find the breakeven point when comparing the CRD to V6 or Hemi or to find out what a particular road trip will cost you.
Then on a separate tab, there's a loan calculator. Enter your MSRP, discounts, down payment, trade, fees, APR, term, etc, and it will calculate your payment. This is useful for comparing interest rates, term, down payment amount, etc.
I hope that some of you find this helpful.