How Do I Measure My Horse For A Bit?
How Do I Measure My Horse For A Bit?
To measure your horse for a bit, use a piece of string or a bit-sizing tool placed in your horse's mouth where the bit would normally sit, mark where it meets the corners of the mouth on both sides, then measure the distance between the marks in inches or millimetres — this gives you the correct mouthpiece width.
Step by step bit measuring
Take a piece of string, a wooden spoon, or a purpose-made bit sizer. Place it gently in your horse's mouth in the same position the bit would sit, resting on the bars of the mouth.
Mark both sides where the string or sizer meets the corner of the horse's lips. Be careful not to pull tight — the measurement should reflect a relaxed, natural mouth position.
Remove carefully and measure the distance between your two marks using a ruler or tape measure. This is your horse's mouth width.
Round to the nearest standard size. Most bits come in sizes such as 4.5", 5", 5.25", 5.5" and 5.75" — choose the closest standard size to your measurement, erring very slightly larger rather than smaller if in doubt.
Common mistakes when measuring
Measuring with the mouth open and chewing rather than relaxed can produce an inaccurate reading.
Pulling the string too tight compresses the lips and gives a measurement that's too small.
Forgetting that mouthpiece thickness also affects fit — two horses with the same width measurement may need different sizes if one has a thicker mouthpiece preference, since extra width is needed to accommodate the additional bulk comfortably.
What if you're between sizes
If your horse measures between two standard sizes, select the smaller size in a fixed cheek without concern, however, it's generally safer to choose the larger size for a loose ring, since a bit that's too narrow pinches the lips, while a slightly larger bit allows a small amount of room for the rings to move freely without discomfort.
Bit Bank Australia offers free sizing guidance with every purchase, and our accredited bit fitters can measure your horse in person if you're still unsure. Find a bit fitter near you or view our size chart.