How to Tell the Age of a Horse

Using Records and Non-Dental Observations

Check breeding, registration, or vet papers for the most accurate age info. If you want to know exactly how old a horse is, you need to check its papers. The date of birth should be listed on any breeding or registration papers connected to a particular horse. If there are no breeding papers, check for veterinary records that indicate the date of birth. For instance, if you’re interested in buying a horse, insist upon seeing any papers that exist. If the horse is registered as a particular breed, it should have papers on file. Contact the relevant breed association if necessary. Not all horses have breeding or registration papers. However, most horses do have veterinary records, so ask to see these.

Have a vet scan a found horse’s neck for an identifying microchip. Many owners have their horses microchipped at an early age so that they can be identified if lost. If you find a horse, contact an equine vet to see if they can scan it for an identifying microchip. In addition to ownership info, the chip should also reveal the horse’s age. If you're interested in buying a horse that has been microchipped, consider asking if you can have it scanned. This can help confirm any paper records or other information on the horse. If you buy a horse without a microchip, get it microchipped a soon as possible. If it has previously been microchipped, have a vet either update the information on the chip or replace the chip.

Look for a brand on a found horse and identify its owner for info. Despite other options like microchipping, some owners still brand their horses. This marking can help you track down a lost horse’s owner and, in turn, find out the horse’s age. If you don’t recognize the brand, ask other horse owners in the area, visit nearby stables, and ask around at equine vet offices and horse supply stores.

Check for a lip tattoo if the horse is a thoroughbred. Thoroughbreds who have retired from the racetrack often have a tattoo on the inside of their upper lip. They get the tattoos when they are young, and the information goes into a racehorse database where you can look up horses by their tattoos. This is a very accurate way to find out when your off-the-track thoroughbred was born.

Use physical signs to make a very general age estimate. As horses age, they typically develop gray hair, lose muscle tone, and develop sunken spots over their eyes, among other common physical changes that often occur at around 18-24 years of age. Factors like these can help you differentiate an “old” horse from a “young” one, but are less helpful in pinpointing a specific age. Estimating age based on size or weight is largely a guessing game. Many horses reach 90% of their final height and 75% of their final weight by 18 months of age. To get a more accurate estimate based on physical observation, rely on methods that involve inspecting the horse’s teeth.

Checking for Dental Grooves on Adult Horses

Look for dark vertical grooves on the top left and right corner incisors. Starting at around age 10, you’ll be able to notice a brownish vertical groove developing along the gumline of the 2 top corner incisors. This line, known as Galvayne’s Groove, appears and disappears incrementally between ages 10 and 30. The incisors are at the front of the horse's mouth, and are all clearly visible when the horse's lips are moved out of the way. “Galvayne’s Groove” is named for a 19th century Australian who used this indicator to age horses with surprising accuracy. That said, Galvayne’s Groove is best used to estimate a horse’s age within a range of about 4 years between the ages of 10 and 30. You can find images of Galvayne’s Groove online to help you recognize it.

Track each groove’s emergence from the gumline down (ages 10-20). During this 10 year period, the grooves on the top corner incisors will extend down the tooth bit by bit. By age 15, the groove will be roughly halfway down each incisor. By age 20, it should reach the tip of each tooth. The horse’s teeth will continue to darken over time, but Galvayne’s Groove should remain dark enough to be clearly noticeable.

Watch for each groove to disappear from the gumline down (ages 20-30). After taking roughly 10 years to fully appear, Galvayne’s Groove will slowly disappear over 10 years. Starting at about age 20, the groove will begin to fade, starting at the gumline. By about age 25, the groove will only be visible on the bottom half of each tooth. At around age 30, Galvayne’s Groove will be completely gone.

Average your estimates for the left and right incisors. When checking the corner incisors, you’ll probably notice that Galvayne’s Groove isn’t in the exact same position on each. In this case, average out the location of the grooves on both teeth to make your age estimate. For instance, say the groove is 40% down the left incisor and 50% down the right incisor. Average this out to 45% and estimate an age of 14.5 years. Or, say the right groove is 60% gone from the top and the left groove is 80% gone from the top. In this case, the average is 70% and the age estimate should be 27.

Observing Other Dental Characteristics

Check for the eruption of milk teeth from birth to 9 months of age. A newborn foal’s milk teeth (that is, deciduous teeth or “baby teeth”) usually start to erupt through its gums between 1-2 weeks of age. The central incisors usually erupt from the gums first. Since they're located at the front of the mouth, you'll be able to see all of the incisors when the horse's lips are moved out of the way. Milk teeth are smaller and whiter than permanent incisors, which have more of a yellowish color and typically reach around 4–5 in (10–13 cm) in length, including the roots. A foal usually has a complete set of 24 milk teeth by 9 months of age, but not all of the teeth may be long enough to show signs of wear yet.

Watch for dental landmarks from ages 1 to 5. These early years make up the period when you can most accurately tell the age of a horse by its teeth. During this time, the horse’s full set of milk teeth will be replaced by permanent adult teeth. At 1 year of age, all the milk teeth should have erupted, but the corner milk incisors will still be too short to show wear. The teeth will be very white. At 2 years old, the corner milk incisors should meet their opposites (that is, the top and bottom incisors should touch) and show wear. Incisors are used to cut and chew grass and other foods. At age 3, the milk teeth in the center (the center incisors) will fall out and be replaced by adult incisors. Adult teeth are bigger (around 4–5 in (10–13 cm) long, including the roots) and yellowish in color. At 4 years of age, the center and intermediate milk incisors will be replaced by permanent teeth—only the top and bottom corner incisors will still be milk teeth. At age 5, all the incisors, top and bottom, should be adult teeth.

Keep looking for dental landmarks between ages 5 and 20. It becomes a bit more difficult to tell a horse’s age by its teeth once all the milk teeth are gone, but there are still several things you can watch for. From ages 5-7, the adult teeth should begin to show clear signs of wear, but the chewing surface of the incisors should be concave. The teeth shouldn’t project outward much if at all yet. At around age 7, the upper corner incisors will develop spurs or hooks where they overhang the lower incisors—this is called the “7 year hook.” It typically disappears by age 8. By around age 9 or 10, the cupping (concave shape) on the chewing surface of the incisors will grow out and leave behind lighter-shaded marks. These marks will typically disappear by age 12. After age 12, and especially after age 15, the incisors will elongate, develop a chisel-like edge, and project outward.

Examine the teeth of a senior horse (age 20-plus) for age clues. If you look into an older horse’s mouth, you’ll know where the expression “long in the tooth” comes from. The horse’s incisors will keep getting longer, meaning that the top and bottom rows will meet at ever sharper angles. The elongated teeth will develop a sloping shape on the outside surface, and will become darker yellow or brown in color. Some teeth may start falling out at around age 25. However, a horse that has received improper care or a poor diet may lose teeth at a younger age.