tire size calculator

[man o jeep]

Does anyone know how I can find out what my OD gear and my axle gearing ratio are? 

[squat]

That info is quite often in the brochure for your vehicle.  You can take the gear box apart and divide the two numbers together or you can count how many tire rotations you are doing.  Those are difficult and time consuming though, I would try to find documentation on your vehicle about this. 

[hemiram]

The gear ratio is also stamped on the gears themselves when you take the gear box apart.