When you’re talking about a saddle’s size, you’re talking about two different measurements—one for the saddle tree and another for the saddle seat.  The dimensions indicated by the tree size apply only to the front of the saddle, specifically the distance between the points of the inverted U shape comprising the head and pommel.

Saddle makers express that distance as degrees, not inches or centimeters, because they are talking about the angle of the inverted U at the front of the saddle tree.  That angle determines the width of the space between the two points resting on the horse, so it’s no surprise that tree sizes refer to both angles and widths.

With English saddles, tree size can be narrow, medium/regular, or wide, with the following angles pertaining to those categories:

• Narrow           =     86 degree angle
• Medium/Regular =     90 degree angle (right angle or perpendicular)
• Wide            =     94 degree angle

This saddle tree size is very important, especially to the health and comfort of your horse.  Besides denoting the angle of the U, the tree size also relates to the measurement of the gullet, an open space or channel underneath the saddle (click here to learn about the gullet in more detail).  So when we talk about saddle tree sizes, we’re talking about not only the angle of the U but also the width of the gullet.

The purpose of this gullet is to keep the weight and friction of the saddle off the horse’s most vulnerable spots, such as the withers and the part of the vertebra that is thin, narrow, and close to the surface (spinous process).  A metal gullet plate occupies the empty space running down the center of the saddle bottom, and the stuffed panels under the saddle keep that part of the saddle up off the horse.

This sounds logical, and it is, but there are two caveats to keep in mind.  First, there are no standard measurements for gullet size, so different saddle makers may use different criteria in sizing (just as one brand of size 8 jeans may be larger than another brand of size 8 jeans).  Second, no two horses are built exactly the same.

That’s why you should inspect every saddle under consideration to ensure that the gullet channel is appropriate.  First, confirm that the gullet width is uniform throughout the length of the saddle, as some gullets get narrower towards the back of the saddle, forming an elongated V shape that will not serve your horse well.

Next, check that the gullet is the right width for the particular horse. Getting the optimum fit involves a bit of a balancing act.  The points of the saddle tree’s U must be far enough apart to clear the horse’s rib cage.  Yet they should not be so wide apart that any force would cause them to press down on the bony and extremely delicate spinous process of the withers.

This is not something you can judge simply by putting the saddle on the horse.  You must simulate real-life riding conditions by test-driving the saddle or at least sitting in the saddle so that your full weight presses on it.

You can also check the width of the gullet with your fingers.  You should be able to fit three fingers into the gullet at the back of the saddle, possibly more if it is a wide-width saddle.

And speaking of fingers, one rule of thumb is that a saddle that is a bit too wide is better than a saddle that is too narrow.  Imagine wearing a shirt that is so tight that it pulls uncomfortably across your shoulder blades, and then further imagine that there are several price tags and dress pins wedged into your back as well, pressing on your delicate areas every time you move. No horse should have to endure a saddle that is too narrow.

Of course, every trip on horseback involves two individuals, one below the saddle and one above it.  To learn about fitting a saddle to make your end of the experience as enjoyable as your horse’s, read our section on the saddle seat.