I was sorting through my bit box last week, as I’ve been selling off some of the bits that I’m unlikely to use again. Since I went bitless with my Trakehner, I have a lot of expensive bits that are now gathering dust!

It got me thinking about bit sizing. There is a lot of discussion on horse forums about saddle fit, but very little about fitting a bit. The irony is, that if you look in tack catalogs, you’d swear that most horses in the world must wear a 5” bit as that’s the predominant size. Looking at my box full of 6” and 5 ½” bits, I’d beg to differ.

In fact, I suspect that many horses are wearing bits that are either too small or too large, probably because so many owners reflexively buy a 5” bit.

The length of a bit depends on the width of your horse’s jaw and the type of cheek and mouthpiece. You can buy a bit fitting tool, or you can start by putting a piece of string through your horse’s mouth and marking the edges of his lips.

Generally, you want about 1/8” of the bit to protrude on either side of the horse’s mouth. If it’s too narrow, it could pinch the sides of his mouth, but if you have too much extra bit, it will move around too much in your horse’s mouth and not act as a good communications tool in your horse’s mouth.

However, you also need to take into consideration the style of the cheek piece. With a fixed cheek piece, like an Eggbutt, a Dee or a Full Cheek, ¼” clearance will work just fine. Not so with a loose ring.

Because the ring rotates on the mouthpiece of the bit, you generally add an additional ¼” to the length of the mouthpiece (so, ½” total); otherwise the bit will pinch the horse’s lips as the ring rotates.

The extra length in the mouthpiece of a loose ring also serves another purpose: the extra length helps the bit to stay centered in the horse’s mouth; if it is too short it can actually be pulled through when the rider pulls on a rein.

Looking through my bit box, I found a 5 ½” loose ring snaffle bit that I used on my old Quarter horse. As you can see, the mouthpiece is not wide enough for my Trakehner gelding, who wears a 5 ½” bit. But it fits my TB gelding perfectly. As a matter of fact, he goes quite well in it!

Making sure that your bit fits your horse’s mouth is an integral part of helping your horse accept contact and be comfortable in his work.