How to Tell a Horse's Age by Its Teeth

"Don't look a gift horse in the mouth" is not a metaphor about manners. It's about price. For most of recorded history, a horse's mouth was its birth certificate — and checking the teeth of a horse you'd just been given was, frankly, rude.

The method still works. It's less precise than sellers like to claim, but a practiced eye can put a horse within a few years of its real age, and that skill still matters for rescue horses, auction purchases, and any animal arriving without papers.

Why teeth work as a clock

Horse teeth erupt on a fairly predictable schedule and then wear down at a fairly predictable rate. Unlike ours, they keep pushing up out of the jaw for most of the horse's life — roughly 2–3mm a year — while grinding against each other. That combination of eruption and wear leaves a readable record.

The four things horsemen look at

1. Which teeth are present (birth to 5 years). This is the most accurate window by far. Milk teeth come in during the first nine months, then permanent incisors replace them on a schedule tight enough to age a young horse within months: central incisors at about 2.5 years, middles at 3.5, corners at 4.5. A "full mouth" — all permanent teeth in wear — arrives around age 5.

2. Cups (5 to 11 years). Cups are the dark hollows in the center of each incisor's grinding surface. They wear away in order — centrals by about 6, middles by 7, corners by 8 — a sequence old horsemen memorized as "six, seven, eight."

3. Galvayne's groove (10 to 30 years). A dark vertical groove appears at the gumline of the upper corner incisor around age 10, reaches halfway down the tooth by 15, extends the full length by 20, then recedes from the top — halfway gone by 25, entirely gone by 30. It's the single most useful marker for aging older horses.

4. The angle of the bite (all ages). Viewed from the side, a young horse's incisors meet almost vertically. As the horse ages, the angle slants progressively forward — a 20-year-old's teeth jut noticeably. This is what people mean by "long in the tooth."

How accurate is it, really?

Honest answer: very good young, rough old.

• Under 5 years: accurate within a few months
• 5–10 years: accurate within about a year
• 10–15 years: accurate within 2–3 years
• Over 15: an estimate, and often off by 5 years or more

Diet is the reason. A horse on sandy pasture wears its teeth faster than one on soft hay and looks years older in the mouth. Cribbers wear their incisors down dramatically. And some unscrupulous sellers have historically filed teeth to fake a younger mouth — a practice called "bishoping."

If a horse has registration papers, trust the papers. Teeth are for when there aren't any.

What this means for your horse's care

Aging by teeth is a party trick. Caring for those teeth is not optional. Because horse teeth erupt continuously, they wear into sharp enamel points that cut the cheeks and tongue. A horse that drops feed, tilts its head while chewing, or loses weight on good hay is usually telling you its mouth hurts.

Get a dental float once a year — twice for horses over 20. It's the single most underrated line item in horse care, and it's a major reason horses today routinely live into their thirties.

Want to know what your horse's age means in human terms? Run it through our horse age calculator, or read the full breakdown of equine life stages in how long do horses live.