Bit Fit: How To Measure a Horse Bit

How do you measure a horse's bit size?

It's not that hard to determine an equine's bit size, even if they've never worn a bit. All you really need is a measuring tool and a length of twine! To put it simply, your horse's bit size is the width of their mouth toward the back, where a bit would naturally sit, plus half an inch. This video shows you how to do it! 


What is a Bit?

Before we dive in to how to determine a horse’s bit size, let’s first explain what a bit is. Did you know bits have been used on horses for thousands of years? Advancement in bit technology and design have come a long way since then, but their function and purpose remain virtually unchanged. An expert rider uses a bit, along with other ‘natural’ aids, such as their voice, legs, and seat to guide a horse and give it commands.

how horse bits work
As long as horses have been domesticated, people have used bits to guide them. (Photo by Jennifer Murray from Pexels)

Bits are typically manufactured from different types of metal, which can then be coated or covered with rubber or plastic for increased gentleness. The bit lays in the bars of a horse’s mouth between its front and back teeth. This positioning prevents the bit from causing discomfort or damage to a horse’s teeth.

Equine bits and their uses

Bits can be used in a variety of ways, but the most common differences in usage involve the way that the reins -- the pieces of leather connected to the bit -- are held by a rider. 

Direct reining, commonly used in English riding, applies pressure on both sides of the bit evenly. If you want your horse to go to the right, your right hand would slightly bring the rein back toward your hip, asking the horse to move his head, and body, in that direction. Same with the left, using your left hand to pull the left rein back toward your hip. 

The other common type is neck reining, which is usually used in western riding. This allows the rider to use only one hand to ride with, leaving the other free for work. In neck reining, the horse moves away from the pressure that the rein gives when it is lightly laid on their neck, and puts very slight pressure on the bit.

Horse Bits Explained

There are two major kinds of bits, the snaffle bit and the curb bit, and beyond these, there are countless variations. The snaffle is the simpler bit, consisting of only a cheekpiece and a mouthpiece.

snaffle bit for horses
A snaffle bit for horses. Photo by Hannah Jones.

The snaffle bit tends to put less pressure on the horse’s mouth. When you give two pounds of pressure, the horse feels two pounds of pressure. Some variations on the snaffle bit include the full cheek, eggbutt, D-ring, and loose ring.

The other major type of bit is the curb bit, which consists of the cheekpiece, curb chain, shank, and mouthpiece. The curb bit shank uses leverage to put pressure on not only the horse’s mouth, but also the poll. This design can increase pressure by four times depending on its size.

curb bit for horses
An equine curb bit. Photo by Hannah Jones.

An equine curb bit. Photo by Hannah Jones.If a rider were to apply two pounds of pressure on the bit, it would give up to eight pounds of pressure depending on the size of the shank. All bits should be used with care, but a curb bit should only be used on a well-trained, high-level horse; if used improperly it can cause serious damage to a horse. 

Some horses don’t require or use a bit at all. Bitless riding prevents heavy-handed riders from hurting their horses’ mouths, and allows trail horses to snack and drink without the need to change to a halter mid-ride. Not all horses are capable of riding without a bit; it takes a gentle and willing horse to comply with this type pressure. Sidepull, bosal, hackamore, and other bitless bridles utilize pressure points on the nose to help guide and direct the horse.

How to measure for a bit

If you are unsure about what size bit your horse might need, you just need a few simple tools and a little bit of patience to figure it out. These tools are:

  • a measuring tape
  • bailing twine or string
  • a marker

You’ll want to make sure your horse is tied up or being held by someone else, because you are going to need both hands for this exercise. Take your string and put it horizontally in your horse’s mouth. Hold it all the way back toward the corners of the mouth where the bit would lay, and pull it straight for accurate measuring. Make sure to hold the string right up against your horse’s cheeks, and then mark those spots with your marker.

how to measure a horse bit
A properly-sized horse bit should fit comfortably between the cheek and teeth. (Photo by Laila Klinsmann from Pexels)

Now take your handy-dandy measuring tape and measure from one mark to the other on your string, then add 1/2 an inch and that will give you the size bit you need. The average bit size for a horse size is between 5 and 6 inches, but will vary by breed, build, and genetic makeup. Horses and ponies with more refined noses such as Arabs and Welsh Cobs often need bits less than 5 inches.

To put it simply, bit size is the width of the mouth from one side to the other, measured around the corner of their mouth, where a bit would sit, plus 1/2 an inch.

If you already have a bit, how do you figure out its size, and whether it will be compatible with your horse? Using your measuring tape you can simply measure the mouthpiece of the bit between the cheekpieces. Do not include the cheekpieces in this measurement!

Off to fit your bit!

Now you are all set to take your newfound bit fit knowledge (as opposed to fit bit knowledge) and use it to decide on the proper bit size for your horse or pony pal! Do you have additional thoughts about bit fit or other horse-related questions or comments? Let us know! We would love to hear from you!


measure horse bit size