I read an article on how do you measure saddle. This is the link : https://www.reference.com/pets-animals/measure-saddle-seat-size-7e19ddb12150fe5d
There are other articles too on this website.
I hope this helps
I would have a fitter come, however all the affordable used saddles are several hours away so I am looking for his general size so I can make an estimated guess when looking at saddles in the store and bring one at a time on trial to see if it would work for us.
I don't want to pick out a saddle that fits me, but not my horse!