How to Size a Bit For Your Horse

Equestrians know that a well-fitted bit, as well as your hand, leg and seat aids, helps control your horse’s neck and head, and can aid in bringing his body into proper alignment. Learning how to fit a new bit properly to your horse is an important part of keeping your horse happily working at whatever job he is performing, and keeping yourself safe in the saddle.


You’ll only need three items for this task: an unsharpened wooden pencil, a permanent marker, and a ruler. *Note: You can also cut a 12-piece of ½-inch garden hose to use instead of the pencil if you think your horse might bite down and break the wood.

With your horse haltered and in cross-ties or tied in his stall, insert the wooden pencil in his mouth, just as you would a bit. Position the pencil on the “bars” of the gums. The bars are the open spaces between the premolars and the canine teeth on both upper and lower jaws where your bit normally rests.

Make a slash with your permanent marker on either side of the pencil at the points where your horse’s lips lie when his mouth is closed. Measuring the distance between the two points gives you the size of the bit needed for your horse.

Note that bits are sized in increments of ¼-inch and ½-inch. If your horse’s mouth measures in between sizes, go up in size to the nearest ¼-inch.



When finding the correct bit for your horse, you also need to consider the shape of the inside of his mouth and his tongue. Large, thick bits are considered softer for the mouth and easier on the horse, but may not work for an animal with a smaller muzzle or dropped palate. Thin mouthpieces or bars on a bit, while often used to exert more control, can cut into a horse’s gums and tongue if used improperly or in heavy hands.

Make sure that your new bit measures long enough so that the rings or shank doesn’t pinch the corners of your horse’s mouth. A bit that is too small can result in open sores on the lips, and be painful to the animal while you’re riding. On the other hand, a too-large bit can move around in your horse’s mouth causing bruising on the upper palate (the roof of the mouth), the gums, and the tongue.



A horse with a well-fitted bit relaxes his mouth, head, and neck, and will move forward freely when asked. He will hold the bit quietly in his mouth without moving it around or chewing on it, and will keep his head quiet and still. If you know your bit is fitting correctly, and yet your horse continues to resist moving forward or appears uncomfortable in the mouth, watch your hands and how you use them. Any bit combined with heavy, restraining hands can cause pain and opposition, and its up to you as the rider to work with your horse, not against him.