How to Tell Horses Age by Teeth – A Simple Guide

Ageing a horse by its teeth (or aging, in American English) is one of the oldest and most useful field skills in horse ownership. When papers are missing, a passport has been lost or a rescue horse turns up with no history, the teeth give you a working estimate. The method is not exact and modern veterinary research has tempered older claims about it (more on the accuracy debate below), but a careful look at the incisors will tell you whether you are looking at a three-year-old, a teenager or a 25-plus veteran. This guide covers the British way of ageing horses by teeth, the year-by-year incisor signs, Galvayne's groove, and the limits of the method.

How accurate is dental ageing in horses?

Older textbooks (and the famous Galvayne diagrams from the 1880s) implied that the teeth give a reliable age right up into the late 20s. Modern equine dentistry takes a more cautious view. A 2025 review by The Equine Practice Company in the UK summarised it bluntly: dental ageing accuracy decreases significantly after five to seven years of age, and beyond ten years any single sign should be treated as a rough indicator rather than a precise reading. Diet, breed, hard versus soft feed and individual variation all change wear patterns. Treat the dental estimate as one piece of evidence alongside body condition, eye depth, hollows above the eyes, the back, and any paperwork the horse came with.

The best place to start is with the incisors at the front of the mouth. These are the teeth most often used for ageing. In foals and young horses, you look at which teeth have erupted and which baby teeth are being replaced. In older horses, you focus more on wear patterns, the shape of the chewing surface, the angle of the incisors, the presence of dental stars, the appearance of hooks and the progress of Galvayne’s groove.

A good example is a horse with all permanent incisors in place and wearing evenly. That horse is likely close to five years old. A horse with no cups left in the lower incisors and visible dental stars is older, often in the eight-to-ten-year range. A horse with a clear Galvayne’s groove halfway down the upper corner incisor is usually around 15 years old.

Baby Teeth and the Early Years

Deciduous teeth in foals

Foals are born without incisors or with the central baby incisors already present. If they are not there at birth, they usually erupt within the first eight days. The intermediate baby incisors come in by about eight weeks, and the corner baby incisors by about eight months. This is why many horse people remember the simple pattern of 8 days, 8 weeks and 8 months.

These first teeth are deciduous teeth, also called milk teeth. They are smaller, paler and shorter than permanent teeth. They are also wider than they are tall, which helps distinguish them from adult incisors. If you look into a young horse’s mouth and see pale, short incisors with that softer look, you are dealing with baby teeth rather than a mature set.

When permanent teeth replace baby teeth

Permanent incisors start replacing baby incisors in a clear sequence. The central incisors erupt at about 2½ years, the intermediate incisors at about 3½ years and the corner incisors at about 4½ years. By about five years old, the permanent incisors are in place and in wear, which makes this one of the easier ages to identify.

This stage is useful because eruption times in horses under five are considered fairly accurate ageing markers. For example, if a horse has permanent central incisors but still has baby intermediates and corners, it is likely around 2½ to 3 years old. If the corners are just coming through, the horse is likely near 4½ years old.

How Adult Teeth Change With Age

Cups and what they tell you

Once the permanent teeth are in wear, one of the first things to study is the cup. A cup is the dark, indented area in the centre of the grinding surface. As the horse chews, the cups wear away in a set order. On the lower incisors, the cups disappear from the centrals at about six years, the intermediates at seven years and the corners at eight years. On the upper incisors, the cups usually disappear at about nine, ten and eleven years.

This means a six-year-old horse may still have cups in some lower incisors, but not in the lower centrals. By eight years, the lower incisors are smooth of cups. By the time a horse reaches around 12 years, all cups are gone and people may describe it as “smooth mouthed”.

Dental stars and enamel spots

After the cups start disappearing, dental stars become more useful. These are linked to the pulp cavity and appear on the grinding surface as wear continues. They show first in the central incisors at about eight years, then in the intermediates at nine years and the corners at ten years. At first they can look more like a line or a narrow mark, then they become darker, rounder and more obvious with age.

An enamel spot may remain after the cup has worn away, which can confuse beginners. The key is to look at position and shape. Cups sit more centrally and wear out. Dental stars tend to appear closer to the front of the tooth and become more defined over time.

Tooth Shape, Length and Angle

Shape of the chewing surface

Tooth shape changes steadily as a horse ages. Younger horses tend to have a more rectangular grinding surface. From about nine years into the mid-teens, that surface becomes more rounded. In later teens and beyond, it becomes triangular, and eventually more rectangular again in very old horses according to classic ageing descriptions.

This is one reason experienced horse people look at the whole pattern instead of one single sign. A rounded table with dental stars suggests a middle-aged horse. A triangular table with a marked angle and Galvayne’s groove suggests an older horse.

Why older horses look “long in the tooth”

The phrase “long in the tooth” comes from the way incisors appear as horses age. In young horses, less tooth is visible below the gum line and the incisors stand more upright. In older horses, more of the tooth shows, and the incisors slope forward at a steeper angle.

For example, if you compare a six-year-old and a 20-year-old from the side, the younger horse usually has a shorter, more vertical incisor profile. The older horse often shows a longer exposed tooth and a more slanted bite angle. That does not give an exact age on its own, but it adds useful context.

Special Markers in Older Horses

The seven-year hook and later hook

A hook can appear on the rear edge of the upper corner incisor. It is often seen around six to seven years and may appear again around 11 to 13 years. Because it can come and go, and because not every horse shows it clearly, it should be treated as a supporting clue rather than a final answer.

This is a good example of why ageing by teeth is an estimate. One horse may show a clear hook, while another of the same age may not. It helps to pair the hook with other features such as cups, stars, tooth shape and angle.

Galvayne’s groove

Galvayne’s groove is one of the best-known markers in older horses. It appears on the outer surface of the upper corner incisor near the gum line at about 10 years. At around 15 years it reaches halfway down the tooth. At about 20 years it runs the full length. By roughly 25 years, the upper half has disappeared, leaving the lower half visible, and by around 30 years it may be gone completely.

If you are checking an older horse and you see a groove just beginning at the gum line, you may be looking at a horse close to 10. If the groove reaches halfway, think around 15. If it runs top to bottom, think around 20. This marker is helpful, but still best used with the rest of the dental picture.

Why Horses Age by Teeth Is Not Exact

Wear is affected by more than age

The reason Horses Age by Teeth is a useful phrase but not a perfect rule is that wear does not happen at the same rate in every horse. Diet, grazing surface, genetics, vices, basic dental care and general management all affect how quickly teeth flatten and change. A horse grazing sandy ground may wear teeth faster than one eating softer forage from another environment.

That is why teeth are usually best for estimating an age range rather than naming an exact birthday. A horse under five can often be aged quite closely. A horse over 10 may only be placed into a broader bracket unless the mouth is very typical and well preserved.

Extra teeth and dental care

Some horses also develop canines, called tushes, and some have wolf teeth. Canines usually appear at about four to five years and are more common in males, though mares may have them too. These teeth are not the main ageing markers, but they can support your assessment.

Regular dental care matters as well. Because horse teeth wear through most of the horse’s life and do not always wear evenly, annual checks by a vet or equine dentist are recommended. A floated mouth may look and function better, but maintenance can also change what an untrained eye expects to see.

A Practical Way to Read a Horse’s Mouth

Start young, then move older

When you examine a horse, begin with the simplest question: are these baby teeth or permanent teeth? If baby teeth are still present, use eruption and shedding times first. If all permanent incisors are in wear, move on to cups, stars and shape. Then check the side view for angle and visible tooth length. After that, look for a hook and Galvayne’s groove.

A practical example helps. If you see permanent corners just in wear, the horse is likely about five. If lower cups are gone, stars are appearing and the table is starting to round, the horse may be around eight to ten. If the teeth are angled, triangular and the Galvayne’s groove is halfway down, the horse is likely in the mid-teens.

Use more than one sign

The strongest method is to combine several signs rather than rely on only one. Cups alone can mislead. A hook can disappear. Galvayne’s groove is useful, but not every horse reads like a textbook. The most reliable estimate comes from matching eruption, wear, stars, shape, angle and groove patterns together.

Horses Age by Teeth remains one of the most practical ways to estimate age when records are missing. It works best when you treat the mouth as a set of clues rather than a single answer. Learn the order of eruption, understand how wear changes over time, and compare several features at once. That approach gives you the clearest reading of the horse in front of you.

Year-by-year incisor chart for ageing a horse by teeth

The British vet school short version (used in BEVA and BHS courses) of the key dental milestones, useful as a quick reference when working through a horse you do not know:

UK and SA passport rules and dental ageing

Since 2009, every UK horse must have a passport recording its date of birth. In theory this should make dental ageing redundant, but in practice passports are lost, stolen, swapped or estimated for older horses imported before the scheme started. Welfare charities such as the RSPCA, Redwings and World Horse Welfare see large numbers of "passport-less" horses each year, and dental ageing is still the standard first-pass estimate before any further investigation. South African horses do not have a UK-equivalent passport requirement, so dental ageing is even more relevant for buyers, vets and welfare officers in SA.

Related Bit and Bridle resources:

• Horse dentition explained — full guide to the equine mouth, EOTRH and routine dental care.
• Wolf teeth in horses — the small extra teeth that often need removing for bitted work.
• Equine canine teeth — why male horses have "tushes" and mares mostly don't.

Galvayne's groove and why modern vets are sceptical

Galvayne's groove is a brown vertical line on the labial (cheek) side of the upper corner incisor. Sydney Galvayne, a 19th-century horseman, claimed it appeared and progressed at fixed ages. Modern research, including the often-cited 2002 study by Richardson at Liverpool Vet School, has shown the groove is far less reliable than the original claims. It varies between breeds, sometimes appears earlier than nine, sometimes never properly forms, and the "wears away from the top" pattern from 20 to 30 is highly inconsistent. The groove is still useful as a rough indicator but should always be checked against the rest of the mouth and the horse's body.

Other signs in older horses

• Tooth angle (profile view). The angle between upper and lower incisors becomes increasingly acute (pointing forward more sharply) with age.
• Cross-section shape. The chewing surface of an incisor changes shape with age, from oval in a young horse, to round in middle age, to triangular by the late teens, and finally back to oval (but longer front-to-back) in horses over 25.
• Length of tooth visible below the gum. Older horses appear to have "long teeth" because the gums recede and the tooth has continued to erupt over decades.

Frequently Asked Questions