Milk incisors come in at about 1 week, 6 weeks and 6–9 months; permanent incisors at about 2½, 3½ and 4½ years. Lower cups wear away at about 6, 7 and 8 years. Galvayne's groove appears at about 10, is halfway down at 15 and full length at 20. After about 10 years, teeth give only a rough range.
How to tell a horse's age by its teeth
Looking in a horse's mouth is the oldest way to judge its age, and it's still what vets do when a horse has no papers. Estimating horse age by teeth works because a horse's incisors come in on a fairly regular schedule, and then wear down and change shape at a fairly steady rate throughout life. Horsemen describe four main clues: when the permanent teeth come in, when the "cups" in the biting surface wear away, the angle at which upper and lower incisors meet, and the shape of each tooth's biting surface (University of Missouri Extension). Older horses add a fifth clue — a dark line on the upper corner tooth called Galvayne's groove.
Only the 12 front teeth (incisors) are used — six on top and six on the bottom. On each jaw they're named from the middle outwards: two centrals, two intermediates and two corners.
The estimator above turns what you see into an age range. Each sign you pick matches an age range from the extension guides; the calculator then finds the age where your answers agree best. Because some signs are more trustworthy at certain ages, it weights them by age band: tooth eruption counts most for young horses (the AAEP guide calls it the most accurate indicator and the only one used under five), cups and tooth shape count most in middle age, and Galvayne's groove and the angle of the teeth count most for older horses. If your answers conflict, it tells you and shows the best combined estimate.
Horse teeth age chart
This horse teeth age chart sums up what you should expect to see at each age. It combines the timelines published by Utah State University Extension, the University of Missouri, Colorado State University and the AAEP's aging guide (reproduced by USDA APHIS). Treat each row as the typical age — individual horses vary by a year or more, and the variation grows with age.
| Approx. age | What you see |
|---|---|
| Birth – 1 week | Milk (deciduous) central incisors erupt |
| 4–6 weeks | Milk intermediate incisors erupt |
| 6–9 months | Milk corner incisors erupt — all 6 milk incisors by about 9 months |
| 1 year | All milk incisors visible; centrals show wear |
| 2 years | Milk incisors worn smooth; corners in full wear |
| 2½–3 years | Permanent central incisors erupt (bigger, with vertical grooves) |
| 3½–4 years | Permanent intermediate incisors erupt |
| 4½–5 years | Permanent corner incisors erupt — "full mouth" at 5 |
| 6 years | Cups gone from lower centrals; upper corner may show a small hook |
| 7 years | Cups gone from lower intermediates; the "7-year hook" may appear |
| 8 years | Cups gone from all lower incisors; dental star in lower centrals |
| 9 years | Cups gone from upper centrals; lower centrals turn round |
| 10 years | Galvayne's groove appears at the gum on the upper corner |
| 11 years | Cups gone from all upper incisors ("smooth mouth"); hook may return |
| 13 years | Galvayne's groove about a third of the way down; centrals becoming triangular |
| 15 years | Galvayne's groove about halfway down |
| 16–18 years | Lower centrals triangular; dental star round and central |
| 20 years | Galvayne's groove full length; incisors slope sharply forward |
| 25 years | Top half of Galvayne's groove has grown out |
| 30 years | Galvayne's groove gone |
Milk teeth vs permanent teeth
Like people, horses have two sets of incisors. Milk (deciduous) incisors are small and white, with a clear "neck" where they narrow at the gum and only a shallow cup. Permanent incisors are larger, broader, more yellow and have vertical ridges and grooves on the front. When a permanent tooth pushes up, it can leave the worn milk tooth sitting on top of it like a cap — which is why shed milk incisors are called "caps".
| Incisor | Milk tooth erupts | Permanent tooth erupts |
|---|---|---|
| Centrals (1st incisors) | Birth – 1st week | About 2½ years (in wear by 3) |
| Intermediates (2nd incisors) | 4–6 weeks | About 3½ years (in wear by 4) |
| Corners (3rd incisors) | 6–9 months | About 4½ years (full mouth by 5) |
A simple rule of thumb from the University of Missouri: the milk incisors come in pairs at about 8 days, 8 weeks and 8 months, and the permanent ones at about 3, 4 and 5 years. Utah State gives slightly earlier ages for the permanent teeth (2½, 3½ and 4½ years), and Colorado State lists 2½–3, 3½–4 and 4½–5 — the difference is mostly whether you count the day the tooth breaks through the gum or the day it meets its partner and starts to wear. A recent study summarised in the AAEP guide also found that incisors may be shed later and over a wider range than traditionally taught. Once all six permanent incisors are in wear, at about five, the horse has a "full mouth".
Cups and the dental star
A new permanent incisor has a deep, dark hollow in its biting surface called the cup — the open top of an enamel fold (the infundibulum). As the tooth wears, the cup becomes shallower and finally disappears, leaving a ring of enamel (the "mark"). Cups wear away from the middle outwards, lower teeth first:
| Incisor | Lower cup gone | Upper cup gone | Dental star appears (lower) |
|---|---|---|---|
| Centrals | 6 years | 9 years | 8 years |
| Intermediates | 7 years | 10 years | 9 years |
| Corners | 8 years | 11 years | 10 years |
When the cups are gone from all 12 incisors — at about 11 years — the horse is said to have a "smooth mouth" (Missouri Extension). The dental star is a yellow-brown line of secondary dentine that seals the pulp cavity; it shows up in front of the cup, and with age it becomes a round dark spot in the middle of the tooth. Utah State and Colorado State give star ages of 8, 9 and 10 years, but the AAEP guide reports it can appear earlier — in the centrals as early as five. The AAEP also warns that cups are less exact than older books suggest: the central cup can be gone by five, while corner-cup remnants can linger until 12–15. That's why the estimator treats cups as a strong sign for horses of about 5–12 and a weaker one outside that band.
Shape of the incisor table
The table is the flat biting surface of an incisor. Because each incisor is wide at the top and narrow and deep further down its length, the shape of the table changes as the tooth wears and erupts:
| Table shape | Typical age |
|---|---|
| Oval (wide side to side) | Young adult, up to about 9–10 years |
| Round | About 9 to the mid-teens |
| Triangular | About 16–18 years |
| Longer front to back than wide ("biangular") | About 18–20 years and older |
The shift from oval to round to triangular is gradual and a bit subjective, but the AAEP calls it fairly reliable: oval to round fits five to nine years, round to triangular 10–15, and triangular to "biangular" (deeper front to back than it is wide) 16–20. Look at the lower centrals first; the intermediates and corners follow a year or two later.
Galvayne's groove horse teeth age chart
Galvayne's groove is a dark vertical groove on the outer face of the upper corner incisor. It's the classic sign for older horses because it grows down the tooth over about ten years and then grows out over the next ten. Utah State, Missouri and Colorado State all give the same timeline:
| Horse age | What the groove looks like | Estimator range |
|---|---|---|
| About 10 years | Appears at the gum line at the top of the upper corner incisor | 10–14 yrs |
| About 13 years | Reaches about a third of the way down (AAEP) | 10–14 yrs |
| About 15 years | Reaches about halfway down the tooth | 14–17 yrs |
| About 20 years | Runs the full length of the tooth, gum to biting edge | 18–22 yrs |
| About 25 years | Top half has grown out; only the lower half remains | 22–28 yrs |
| About 30 years | Groove has grown out completely | 28–40 yrs |
The AAEP guide adds an important caution: the groove is not present in every horse, it may or may not be stained dark, and even when it is there, its length is only a rough guide to age. It may first show at nine rather than ten. So a horse with no groove could be under ten, over 30 — or simply one of the horses that never shows one. The estimator treats "no groove" as either under 10 or 30+ and lets your other answers decide which.
The 7-year hook and the angle of the incisors
From the side, some horses show a small notch or hook on the back edge of the upper corner incisor, where the lower corner doesn't meet it fully. Traditionally it appears at about seven, disappears within a year or two and may come back at 11 (Utah State) or 12–15 (Missouri). The AAEP guide considers the hook too inconsistent to be useful on its own, so the estimator gives it very little weight — it can nudge an estimate but never decide one.
The angle of the incisors is more useful for telling a young horse from an old one than for pinning down an exact age. In a young horse the upper and lower incisors meet almost in a straight line — about 160–180° seen from the side. With age the teeth slant forward and outward; by around 20 the angle is sharply less than 180° (the AAEP puts it near 120° or less), and the lower incisors usually slope first.
Why horse teeth and age don't always match
Teeth are a good guide for young horses and a rough one for older horses. The University of Missouri says the chance of error grows with age and that aging becomes "a guess" after 10 to 14 years; the AAEP guide agrees that changes from 15 to 20 are gradual and less accurate than in horses under ten. Several things change how fast teeth wear:
- Diet and grazing: stabled horses tend to look younger than they are, while range horses grazing sandy ground look older because grit wears their teeth faster (Missouri Extension). Utah State notes that what a horse eats changes the timeline.
- Vices such as cribbing: cribbing — biting on fences or stable doors — chips and wears the front incisors and can make a horse look older.
- Dental work and bite problems: floating, reducing overlong incisors, overbites and underbites all change the surfaces you're reading.
- Breed and individual variation: the AAEP notes that cups, marks and table shapes vary a great deal between breeds and individuals.
For those reasons, use the estimate as a range, not a birthday. After about 10 years, teeth can only place a horse within a span of several years. An equine vet or qualified equine dentist can combine the teeth with the rest of the horse's condition for a better estimate.
How to look at a horse's teeth safely
- Only check the teeth of a calm horse you know, with someone holding it on a headcollar and lead rope in a safe, quiet place.
- Stand to the side of the head, never directly in front, and keep your fingers away from the biting surfaces.
- To see the incisors, gently part the lips with your thumb and fingers; you don't need to open the mouth. For the side view (hook, angle, Galvayne's groove), look from beside the head.
- Never put your hand between the back teeth. Checking molars, using a mouth speculum or any dental work is a job for your vet or equine dentist.
- If the horse is head-shy or unsettled, stop and ask a professional — a sedated exam is safer for everyone.
Once you have an age range, convert it with the horse age calculator to see your horse's age in human years, life stage and care tips.
Frequently asked questions
How do you tell a horse's age by its teeth?
Look at the incisors. Up to about five, check which milk and permanent incisors have come in. From about 5 to 11, check which cups have worn away and the shape of the biting surface. After 10, look for Galvayne's groove on the upper corner incisor and the angle of the teeth from the side. The estimator above combines these signs for you.
How old is a horse with a full mouth?
A "full mouth" means all six permanent incisors are in, which happens at about 4½–5 years. On its own that only tells you the horse is 4.5+ years old (about 21.8+ in human years); check the cups next.
How old is a horse whose cups are gone from the centrals and intermediates?
If only the lower corner incisors still have cups and all the adult teeth are in, the horse is typically 7–8 years old — about 28–30.5 in human years. This is also when the 7-year hook may appear.
How old is a horse with a smooth mouth?
When cups are gone from all upper and lower incisors (a "smooth mouth") the horse is usually 11+ years old. From here on, Galvayne's groove and tooth shape give better clues.
At what age does Galvayne's groove appear?
It usually appears at the gum line at about 10 years (the AAEP says 9–10), reaches halfway at about 15 and the full length at about 20. A groove about halfway down suggests a horse of roughly 14–17 years (about 45.5–53 in human years).
What does a Galvayne's groove horse teeth age chart show?
It shows how the groove on the upper corner incisor changes with age: appears near 10 years, halfway down at 15, full length at 20, top half grown out by 25 and gone by 30.
How old is a horse with a full-length Galvayne's groove and triangular teeth?
Those two signs together point to about 18–22 years — roughly 55.5–65.5 in human years.
How old is a horse with a full set of milk teeth?
A horse with all six milk incisors and no permanent incisors yet is usually between about 9 months and 2½ years old (the estimator shows 0.5–2.5 years).
What is the 7-year hook on a horse's teeth?
It's a small notch on the back edge of the upper corner incisor, traditionally seen at about 7 years. It can disappear and return at 11–15, and the AAEP considers it too unreliable to use alone.
How accurate is aging a horse by its teeth?
Very good for horses under five — tooth eruption is the most accurate sign. Fairly good from 5 to about 10. After 10 to 14 years it becomes a rough estimate, because diet, grazing on sandy soil, cribbing and dental work all change how teeth wear.
Why do different horse teeth age charts give different ages?
Sources measure slightly different things (the day a tooth breaks through the gum vs. when it starts to wear) and newer studies have found more variation than older books. For example, permanent central incisors are listed at 2½ years by Utah State and about 3 years by Missouri.
This calculator gives an estimate for education and fun. Every pet ages differently — for health decisions, talk to your veterinarian.