Here's a calculator, not my favorite, but it will work.
http://www.kabamus.com/garage/gears.html
Gear ratios in the late model cars are as follows:
2.66
1.78
1.30
1.00
.74
.50
I have 3.55s and am quite pleased. BTW, I'm in Laplata, worked on Washingtonian Blvd in Gaithersburg for a...