Instructions
Determine if the teeth are permanent or temporary. A horse's temporary teeth are the equivalent of human baby teeth, and fall out as a young horse matures. Temporary teeth are smaller, shorter and lighter in color than permanent teeth and start to develop when a horse is around 8 weeks old and are typically replaced by permanent teeth when a horse is between the ages of 2 and 3.
Check the shape of the teeth. As a horse ages, the shape of its teeth change significantly. During its youth, a horse's teeth are generally flat and wide. But as the horse ages, the back of the teeth take on an oval shape, typically starting between ages 8 and 12. At around age 15, the teeth may become more triangular shaped.
Look for indentures in the center of the tooth surface. The indentures, which are commonly called "cups," are typically found in horses' young permanent teeth, with the ones in the lower teeth more shallow than those in the upper teeth. Between ages 6 and 11, the indentures gradually smooth out at different times in different sections of the mouth. Most horses' lower teeth are typically smooth by age 9 and the upper teeth smooth by age 11.
Inspect the angle at which the upper and lower teeth meet. The angle at which the two sets of teeth contact is typically about 170 degrees in young horses, but changes as the teeth begin to slant outward when the horse ages. By age 7, this can cause a gap to form between the upper and lower sets of teeth, since at this point they line up unevenly with one another.
How to Tell the Age of Horses Using Their Teeth
Determining the age of a horse by looking at its teeth is an inexact process and can be used to find an approximate, but not exact calculation. Ways to determine the age include examining the shape, color and texture of the teeth, as well as the angle at which the top and bottom sets of teeth meet. The determination process works best on younger horses, since their teeth are more noticeably different than those of fully mature horses.