Every found cat arrives without a birth certificate, and age drives most of the decisions that follow — whether a kitten can be weaned, when to sterilise, what vaccinations are due, and what medical screening makes sense.
You can get surprisingly close with observation alone. Here is how, and where the method stops being reliable.
Kittens: the first eight weeks
This is where estimation is most accurate, because kittens change so fast that each week looks different.
| Age | Eyes and ears | Teeth | Movement | Rough weight |
|---|---|---|---|---|
| 0–1 week | Eyes closed, ears folded | None | Wriggling only | 100–150g |
| 1–2 weeks | Eyes opening, blue | None | Crawling | 150–250g |
| 2–3 weeks | Eyes open, ears upright | Incisors appearing | Wobbly standing | 250–350g |
| 3–4 weeks | Focusing well | Canines appearing | Walking, playing | 350–450g |
| 4–6 weeks | Fully alert | Premolars in | Running, climbing | 450–700g |
| 6–8 weeks | Eye colour changing | Full baby teeth | Confident, coordinated | 700g–1kg |
A rough rule for the first six months: kittens gain roughly 100g a week, and weigh approximately one pound per month of age.
Kitten Lady publishes photographic age comparisons that are worth checking against if you are unsure.
Eye colour is a useful clue
All kittens are born with blue eyes. Adult eye colour develops from around six or seven weeks and settles by about three months.
A kitten with clearly amber, green or gold eyes is almost certainly past seven weeks. Persistent blue in an older kitten simply means the cat is blue-eyed.
Combined with teeth, this narrows the estimate considerably. Our guide to what to do when you find newborn kittens covers why age matters so urgently at this stage.
Teeth: the most reliable indicator
Teeth are the single best evidence available, and they remain useful long after kittenhood.
- 2–4 weeks: baby incisors then canines emerge.
- 3–6 weeks: premolars appear; full set of 26 baby teeth by around 8 weeks.
- 3–4 months: adult incisors replace baby ones.
- 4–6 months: adult canines and premolars come through.
- Around 7 months: full adult set of 30 teeth, clean and white.
After seven months, teeth still help but with much less precision, because wear and tartar depend heavily on diet and genetics rather than age alone.
Adults: where it gets vague
Between roughly one and seven years, cats change very little in appearance. Anyone offering a confident age for a healthy adult cat is guessing.
| Indicator | Younger adult | Older adult |
|---|---|---|
| Teeth | White, minimal tartar | Yellowing, tartar, possible loss |
| Eyes | Clear, bright iris | Slight haze, iris texture changes |
| Coat | Smooth, glossy | Coarser, sometimes patchy |
| Muscle tone | Firm, well covered | Bonier along spine and shoulders |
| Activity | Agile, jumps readily | More deliberate, jumps less |
| Claws | Retract smoothly | Thicker, more brittle |
The honest answer for most adult cats is a range — “probably two to five” — and that is what a good rescue will tell you rather than a specific number.
Signs of a genuinely senior cat
From around eleven years, changes become easier to read.
Look for prominent spine and shoulder blades, a coarser or unkempt coat as grooming becomes harder, cloudiness in the eyes, and reluctance to jump to previously routine heights.
Reluctance to jump is frequently mistaken for age itself when it is usually arthritis, which is treatable. Our guide to how often a cat should see the vet covers what senior screening should include.
Why the estimate matters
- Weaning: kittens under four weeks need formula, not solid food.
- Sterilisation: most clinics fix from around eight weeks and two pounds.
- Vaccination: the kitten series depends on age at each dose.
- Socialisation window: roughly up to eight weeks for straightforward handling.
- Screening: cats over seven benefit from routine bloodwork.
- Diet: growth formulas for kittens, different needs for seniors.
Getting a kitten’s age wrong by two weeks matters far more than getting an adult’s wrong by two years.
For community cats
You will rarely get close enough to examine a feral cat’s teeth, so estimates come from build and behaviour instead.
Ear tips, scarring, jowls in males and general body condition give a rough sense of whether a cat is young, prime or ageing.
The practical moment for a proper assessment is at TNR surgery, when the cat is anaesthetised and a vet can check teeth directly. Ask the clinic for an age estimate on the paperwork — it is useful for your colony records.
Our guide to colony record keeping covers what to log, and telling whether a community cat has already been fixed covers the other assessment made from a distance.
What not to rely on
Some commonly cited indicators are much weaker than their reputation.
- Size: varies hugely between individuals and is a poor guide past six months.
- Grey hairs: cats do not reliably go grey with age the way dogs do.
- Weight alone: tells you about condition, not years.
- Tartar in isolation: heavily influenced by diet and genetics.
- Behaviour: a nervous young cat can act like an old one, and vice versa.
Combine several indicators rather than trusting one. Teeth plus eyes plus muscle tone gives a far better estimate than any single sign.
When it matters clinically, ask a vet. An examination under good light — and bloodwork where relevant — will narrow things considerably further than observation can.
Why rescues give a range rather than a number
An adoption listing saying “approximately three years” is an honest estimate rather than evasion, and it is worth understanding what sits behind it.
For any cat past about seven months, age comes from a vet weighing several imprecise indicators together. A confident single number for an adult cat usually means somebody guessed.
Ask what the estimate was based on. “Teeth and muscle tone suggest three to five” is far more useful than a flat number, and it tells you the organisation is being straight with you.
Our guide to writing adoption profiles that work covers why honest uncertainty beats false precision in a listing.
Frequently Asked Questions
How can I tell how old a kitten is?
Use eyes, ears, teeth and weight together. Eyes closed means under a week; eyes open with folded ears around two weeks; walking and playing by four weeks; full baby teeth by about eight weeks.
What is the rule for kitten weight and age?
Roughly one pound per month of age for the first six months, gaining about 100 grams a week. It is approximate but useful when combined with teeth and eye development.
Do all kittens have blue eyes?
Yes, at birth. Adult eye colour develops from around six or seven weeks and settles by roughly three months, so clearly amber or green eyes indicate a kitten past seven weeks.
Can you tell a cat’s exact age from its teeth?
Accurately up to about seven months, when the full adult set is in. After that, tartar and wear depend heavily on diet and genetics, so teeth give a range rather than a number.
How do you estimate the age of an adult cat?
Only as a range. Between one and seven years cats change very little. Combine teeth condition, eye clarity, coat quality and muscle tone, and expect an answer like “probably two to five”.
How can I age a feral cat I cannot handle?
From build and behaviour at a distance, then properly at TNR surgery when the cat is anaesthetised and a vet can examine its teeth. Ask the clinic to note an age estimate on the paperwork.