How to measure axle-to-axle distance?

The axle is the small "pin" that holds your cams/idler wheel in the limbs. Measure from the center of the top axle to the center of the bottom axle.

This measurement is taken with the limb bolts maxed out (maximum poundage-screwed all the way down) in determining the axle-to-axle distance.

This is your axle to axle distance.

Most manufacturers recommend taking this measurement on the side opposite your shelf (the side where the arrow rests).