Originally Posted by upnover
You measure from the little buttons on the side of the pommel, straight back to the middle of the cantle. That measurement is your size.
that measurement is your SEAT size, not your TREE size. At least how i've been taught, tree size equals the width of the tree (narrow, medium, wide, etc.) and seat size is the length from the saddle nails back to the center of the cantle. *shrug* could all be semantics.
Try this out for measurement info: SADDLE FITTING GUIDE