I was once in a tack shop looking at rows of used dressage saddles. I asked the owner why they were mostly 17″ and 17 1/2″. She told me that people often bought saddles in smaller sizes than they actually needed, mostly, she speculated, out of vanity. “People just don’t want to say that they ride in an 18″ or 19″ saddle,” she said. “They think that it means their butts are too large. Sooner or later they come back and trade it in for a larger size because a saddle that’s too small just isn’t comfortable.”

The irony is, that riding in a saddle that is too small is what makes your butt look big. Since there are no sizes printed on the back of the saddle, I can’t understand why people make such a fuss over buying the right size saddle.

The first step to buying the correct size saddle is to understand what influences rider fit. Hint: it’s not just the size of your butt. It has a lot more to do with the length of your leg from your hip to your knee, the position of the stirrup bars, the position of the flaps and depth of the seat. Depending on the variables you might find that you might feel comfortable in a 17″ saddle in one model but need an 18″ in another. Ideally, you want about one hand’s width between your butt and the cantle of the saddle. How you achieve that fit depends on the construction of the saddle.

The length of the seat you need depends on the length of your hip to your knee. If you have long legs, you either need a longer seat or a more forward flap to accommodate your leg. Sometimes just buying a larger seat doesn’t work because while it provides enough room for your leg, riding in a larger seat isn’t comfortable. Many saddles now come with a variety of flap lengths and positions. If you have a longer femur, you might find that using a long flap or a more forward flap will accommodate your leg without going to a larger seat size.

If you like the security of a deep seat, you will also need a longer seat as the deep seat creates a shorter sitting surface.

People often talk about whether a saddle has a wide or narrow “twist”. This refers to the width of the saddle tree at its narrowest part, right behind the pommel. For the rider, it refers to the width of the saddle between your upper thighs.

The style of twist that is most comfortable for you depends on the shape and position of your pelvis, the way the femur is attached to it and the shape of the inner thigh muscle. If the twist of a saddle is too wide, you might feel stretched through your hips. Also, if have shorter legs, you might find that a narrower twist holds your leg too far away from the saddle.

The placement of the stirrup bars is also important for how balanced you are in a saddle. The bars need to be placed so that your leg hangs down with your ear, shoulder, hip and heel are in line. If they are too far forward, again you sit in a chair seat; if they are too far back, your leg will be too vertical and you will be positioned forward onto the front of your pelvis. Placement of the thigh block can have similar impact — a thigh block too far forward pushes you onto your butt; too far back and it tips you forward onto your pelvis.

The flap of your saddle should be half way down the calf muscle. If it is too long, it interferes with your leg aids. If it is too short, it can catch on the top edge of your boot.

Saddle fit for the rider is a very personal choice. What works for your best friend might be uncomfortable for you. A saddle that fits you well will help you sit correctly without effort; in a saddle that is a poor fit, you will feel like you are fighting the tack — always working to bring your leg either forward or back.

Before buying a saddle, it’s a good idea to ride in as many saddles as you can. It will help you understand what features work for you. Borrow saddles from friends, or go to a consignment shop and take a few home. Usually you will know in just a few minutes whether the saddle is the right one for you.

Keep in mind that your tastes might change over time, too. While you might like a deep seat for security when you start riding, later you might decide that a flatter seat is more comfortable. Or you might go from a more padded saddle to one with smaller knee rolls or a monoflap design if you choose a more close contact feel. Whatever you choose, remember that no one but you knows what size it is, and if it’s the right size, your butt will look just fine.

When I try a saddle, I look for one that balances me naturally on my seat bones and which allows my legs to fall naturally in close to correct alignment. I like to have enough room in the back to fit a hand between my butt and the cantle. Mostly I look for a saddle that makes it easy for me to ride, so that the tack helps me find my position rather than pushing me out of it.