To determine what size seat your saddle is you will first place a measuring tape or ruler in the middle of the top of the gullet straight back to the top of the cantle. You will measure the barrel saddle in niches and how ever many inches the saddle is how many inches the seat is. Now just because your saddle is one size doesn't mean that you fit in that saddle. The most common seat size is a 15 in or 16 in. You want the saddle to fit you a little tight because barrels saddles are made to keep you in the saddle when you go around the barrels or if your horse bucks. This is just so you don't fall off if you get off balance. Some people don't like to have tight saddles they really should have a 14 in but they feel conferrable in a 15 in. Barrel saddles are really good for little kids that do or don't know how to ride simply because it will be more like a car seat. You also want to make sure that it fits your horse in the withers because we don't want it to be uncomfortable for them. There are two types of saddles that will fit your horse ether a full quarter horse bars or a semi quarter horse bars. This this where the saddle is placed on their withers right above their front shoulders. If it looks like the saddle in sitting up high on the withers and when you are ridding the saddle likes to slip then you probably need a full quarter horse bar saddle. I hope that this will help you find a saddle good luck!