Some quick information about saddle fitting,and about the Saddle's Construction

A saddle is built on a tree, either wood or plastic. DUETT saddles are built on a conventional saddle tree: metal-reinforced laminated wood, with "spring tree" - webbed seat for rider comfort. The measurement of the width of a saddle is taken by a manufacturer on the raw tree, before any leather or other materials are added. The tree itself consists of a wood "frame" which provides the seat for the rider; from the pommel arch two metal "arms"
extend; these are the bars of the tree.

When the measurement is taken, it is on a "raw" tree, straight across the bottom, from bar tip to bar tip. The more angled the bars are, the wider the measurement will be. However, there is no absolute standardization in the industry, so some bars are shorter than others. Therefore, two saddles with bars at the same angle could measure quite differently if one had shorter bars than the other one. Therefore, you can't always translate directly between saddles. Saddle X in 32 cm may fit your horse differently than Saddle Y in 32 cm.