how to measure a horse bit

How To Measure A Horse For A Bit: An Expert Guide

Finding the perfect fit for your horse’s bit is like discovering the secret to seamless communication between you and your horse. Plus, it may be the key to ultimate comfort for your horse.

In this handy guide, I’ll walk you through how to choose a bit, what to consider, and how to measure a horse bit. When we’re done, you’ll have an even stronger bond with your horse and have the know-how to measure any type of bit – for any type of horse.

Horse bit

Selecting a Horse Bit

The bit is one of the most important components of a horse’s bridle. And, selecting the right horse bit size is crucial for proper communication and control when you’re riding. The choice of bit depends on several factors, like riding discipline, your experience level, and the horse’s training.

Bits for Beginner Riders

Beginners usually have less refined riding skills and may have difficulty maintaining steady contact with their horse’s mouth. Therefore, a mild bit that encourages a soft and relaxed jaw is the best choice.

A snaffle bit is one of the most commonly used beginner bits. Snaffles are direct-action bits that work by applying pressure evenly across the tongue, bars, and corners of the mouth. Typically, they have a single or double joint with a lozenge or French link in the centre, making for a more comfortable fit.

Snaffle bit

Common Issues with Incorrect Bits

The wrong bit can come with a plethora of problems for the horse and the rider. If a bit is too harsh for an inexperienced rider, it can lead to heavy-handedness and unintentionally harsh actions. This can cause discomfort and anxiety in the horse.

Too much pressure from the wrong bit can cause the horse to toss their head, open their mouth, or lean on the bit. Of course, when these behaviours are paired with mouth injuries and pain, the rider may have difficulties controlling the horse.

So, a correctly fitted bit will not only benefit your horse, but you as well!

Factors To Consider Before Measuring A Horse Bit

The Anatomy and Health of The Mouth

The anatomy of your horse’s mouth can affect your choice and the fit of a bit. Some horses may have mouth or tooth issues like sharp teeth or teeth that are not properly aligned (called malocclusions) which can affect their bit acceptance.

So, before you invest in a new bit, you may want to assess the overall health of your horse’s mouth. If your horse has health issues such as tongue damage, you may want to consider using a bitless bridle like a Hackamore bridle.

Some of the most important parts of the mouth to consider include:

  • The tongue: Just like ours, the horse’s tongue is a highly sensitive muscular organ which plays a crucial role in swallowing. You’ll need to avoid putting excessive pressure on the tongue. Otherwise, the bit may interfere with your horse’s ability to swallow.

  • Horse’s mouth corner and lips: The bit should always be properly positioned to prevent pinching the horse’s lips or rubbing against the corners of the mouth. An ill-fitting or incorrectly positioned bit can cause mouth sores and lead to behavioural issues. The bit should always rest comfortably in the mouth.

  • The temporomandibular joint (TMJ). This small joint how your horse opens and closes its mouth. A horse refusing to take the bit can be a a sign the TMJ is senstivie.

Cheeky cob sticking it's tongue out

Your horses tongue size and shape will have an influence on bit choice

Age and Breed

For a more comfortable riding experience, you’ll need to consider the age and breed of your horse. Younger, less experienced horses may need to start with a gentler bit to improve the chances of acceptance and learning. On the other hand, older and more experienced horses may have specific preferences or needs that you’ll have to take into account.

Additionally, different breeds of horses can have variations in their mouth conformation, sensitivity, and responsiveness. So when you’re picking out a new bit, you’ll want to take time to consider the your horse’s breed characteristics.

The Type Of Horse Bit

  • Weymouth: A Weymouth bit is used as part of a double bridle, which consists of two bits. This bit is designed to work in tandem with a second bit known as a bradoon. When measuring a Weymouth bit, you’ll need to consider the length of the lower shank. This can affect the severity of the bit’s action.

  • Loose Ring Cheeks: These are the sides of the bit that have rings through which the bit’s mouthpiece can move freely. When using a loose ring bit, you’ll need to ensure that there is a 5 mm gap between the edge of the horse’s lips and the bit ring.

  • Fixed Cheek Bits: A fixed cheek bit has cheeks that are attached to the mouthpiece. Unlike a loose ring bit, this bit restricts movement and provides more stability. When you’re picking out a fixed cheek bit, you’ll want to choose one that is one size smaller than loose rings. The most common type of fixed ring is a D-ring or Eggbutt.

Weymouth bit

Weymouth Bit

Horse Bit Materials to use with caution

When choosing a bit, you’ll want to choose high-quality bits made from trusted materials. It’s particularly good to know which bits may be harmful to your horse, including:

  • Plastic: Plastic bits lack durability and can potentially injure your horse’s mouth. They tend to have sharp edges and rough surfaces that can cause irritation.

  • Alloy: While some alloys such as stainless steel are suitable for bits, you’ll need to be careful of generic or low-quality alloy bits. These bits may contain a mixture of various metals that can cause allergic reactions.

  • Black rubber: Rubber bits should be used with caution. They can deteriorate over time and cause the bit to stick to the horse’s mouth or cause chafing.

  • Nickel: Nickel bits may cause allergic reactions in some horses. Horses with nickel allergies may develop mouth sores and irritation.

  • Copper: While copper is a popular bit material because of its taste and salivation-inducing properties, use it with caution if your horse has a sensitive mouths. Some horses may have copper allergies.

How to Measure a Bit for Your Horse

What You Need

  • A bit sizer tool, tape measure, or a string

  • A ruler

  • A pen or marker

Step 1: Measuring Your Horse

Before you pick a bit, you’ll need to measure your horse’s mouth by following these easy steps:

  1. If you’re using a homemade measuring device, make sure to mark off a starting point.

  2. Place the tape measure horizontally between the horse’s lips where the bit would rest (good luck with this!) or place the bit gauge across your horse’s mouth and adjust the width until it fits comfortably.

  3. Measure the distance between the inside edges of the lips.

Step 2: How To Measure the Bit’s Size


  • Mouthpiece width: Measure the distance between the bit ring holes on a flat surface. Place the measuring tape horizontally along the mouthpiece.

  • Thickness: Use a calliper to measure the diameter of the mouthpiece at its thickest point.

  • Lower shank length: Measure the vertical length of the lower shank. This is the part that extends downward from the mouthpiece to where it connects to the curb chain or strap.

Loose Ring Cheeks and Fixed Cheeks:

  • Width: Measure the distance between the inside edges of the fixed or loose ring cheeks. Place the measuring tool horizontally across the rings.

  • Thickness: Use a bit gauge or calliper to measure the diameter of the mouthpiece, remembering to measure at the thickest point.

Tension Issues with Horse Bit Fittings

If a horse bit fits incorrectly, it can cause several tension issues. To be proactive in detecting these issues, you’ll want to look out for signs of distress in your horse. These signs may include behavioural changes like head tossing, or physical changes like bruising on the bars of the mouth, or sores and ulcers.

If your horse is in pain or uncomfortable, it can cause challenges for you, too. You may experience a loss of control of your horse or communication difficulties and less responsiveness. So, if you notice any of the signs, you’ll want to address them as quickly as possible to keep your horse (and yourself) happy and healthy.


What is the average bit size for a horse?

A horse’s bit size depends on the breed, size, and contortion of the horse’s mouth. However, the most common size used for horses is a bit with a mouthpiece width of around 12.7 – 15.2 cm (between 5 to 6 inches).

Is a thicker bit better for a horse?

The thickness of a bit relies on the specific needs of the horse and personal preference. Generally, a thicker bit can distribute pressure more evenly over the horse’s tongue and bars. Horses with smaller or more sensitive mouths may prefer a thinner bit.

Should a horse chew on the bit?

It’s not ideal for a horse to continually chew or play with the bit when they’re being ridden. Continuous chewing may be a sign of tension, anxiety, or resistance. However, some light mouthing can be a positive sign of relaxation and acceptance.

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