Healthy kittens gain about 100 g a week, open their eyes at 1–2 weeks, grow their first teeth at 2–4 weeks and have all 26 baby teeth by 6–8 weeks. Combine weight and teeth for the best estimate.
How to figure out how old a kitten is
Found a kitten outside, adopted one from a shelter, or brought home a stray with no paperwork? You can estimate its age surprisingly well by looking at a few body signs. Kittens develop on a predictable schedule during the first 8 weeks, which is why rescue workers and vets can usually guess a young kitten's age to within about a week.
This kitten age calculator combines the five signs vets and rescue experts use — weight, teeth, eyes, ears and movement — and finds the age range where they agree. Teeth get extra weight because they are the most reliable clue: a sick or underfed kitten may be light for its age, but its teeth still come in on time.
1. Weigh the kitten
Healthy kittens gain about 100 grams (3.5 oz) per week for the first two months, so a 450 g kitten is usually about 3–4 weeks old. After 8 weeks, a handy rule is that a kitten weighs about 1 pound per month of age until around 5–6 months.
2. Look at the teeth
No teeth means under about 2–3 weeks. Tiny front teeth (incisors) appear at 2–4 weeks, the little fangs (canines) at 3–4 weeks and premolars at 5–6 weeks. A full set of 26 sharp baby teeth usually means 6–8 weeks. Adult teeth push through from about 3–4 months, and by 6–7 months a kitten has all 30 adult teeth.
3. Check the eyes and ears
Kittens are born with eyes sealed shut; they open around 8–14 days and are always baby-blue at first. Around 6–7 weeks the adult eye color (green, gold, copper) starts to show. Ears are folded flat at birth, begin to unfold at around 2 weeks and stand upright by 3 weeks.
4. Watch how it moves
Newborns crawl. At about 3 weeks kittens take wobbly steps, by 4 weeks they walk and play, and by 5–6 weeks they run, pounce and climb.
Kitten growth chart: the first year
| Age | Typical weight | Milestones | Teeth |
|---|---|---|---|
| Newborn (0–1 wk) | 50–150 g | Eyes & ears closed; umbilical cord attached | None |
| 1 week | 150–250 g | Eyes start to open around 8–12 days | None |
| 2 weeks | 250–350 g | Eyes open, baby blue; ears unfolding | None |
| 3 weeks | 350–450 g | Ears upright; first wobbly steps | Tiny incisors |
| 4 weeks | 450–550 g | Walking and starting to play | Canines erupting |
| 5 weeks | 550–650 g | Running; learning the litter box | Premolars |
| 6 weeks | 650–750 g | Pouncing; weaning onto wet food | Baby teeth nearly complete |
| 7 weeks | 750–850 g | Adult eye color begins to show | All baby teeth |
| 8 weeks | 850–950 g (~2 lb) | Fully weaned, very playful | All 26 baby teeth |
| 3 months | about 3 lb | Confident, adventurous | Adult incisors start |
| 4 months | about 4 lb | Adult teeth coming in | Mixed teeth |
| 6 months | 5–6 lb | Nearly adult size (breed dependent) | All 30 adult teeth |
| 12 months | adult weight (often 7–10 lb) | Kitten → young adult | Adult teeth |
Weights for the first 8 weeks follow Kitten Lady's widely used rescue guide. Breed, litter size and health all change the numbers — use them as a guide, not a rule.
How to tell the age of an adult cat
Once all adult teeth are in (about 6 months), age gets harder to judge. Vets look at several clues together:
- Teeth: clean, white teeth suggest about 1 year; some yellow tartar suggests 2–5 years; heavy tartar and wear suggest 5–10 years; missing teeth suggest a senior.
- Coat: young cats have fine, soft coats; older cats may have coarser fur and some grey hairs.
- Eyes: young cats have clear, bright eyes; older cats may show cloudiness or a lacy iris.
- Muscle and body: senior cats often lose muscle along the spine and hips.
Once you have an estimate, convert it with our kitten months to human years or senior cat age calculator.
Frequently asked questions
How can I tell how old my kitten is?
Check its weight, teeth, eyes, ears and movement. Healthy kittens gain about 100 g per week, get their first teeth at 2–4 weeks, open their eyes at 1–2 weeks and have a full set of baby teeth at 6–8 weeks. Enter these signs in the calculator above for an instant estimate.
How do you estimate a kitten's age by weight?
For the first 8 weeks, a kitten's weight in grams divided by 100 is roughly its age in weeks (a 450 g kitten ≈ 3–4 weeks). After that, a kitten weighs about 1 pound per month until around 5–6 months.
Can a vet determine the age of a cat?
Yes. A vet can closely estimate a kitten's age from its teeth and development, usually within a week or two. For adult cats the estimate is broader and is based on teeth, tartar, eyes, coat and bloodwork.
How do you figure out a cat's age once it's an adult?
Look at the teeth first: white teeth ≈ about 1 year, some tartar ≈ 2–5 years, heavy tartar and wear ≈ 5–10 years, and missing teeth often mean 10+ years. Coat, eyes and muscle tone add clues.
How old is a kitten when its eyes open?
Most kittens open their eyes between 8 and 14 days old. All kittens have blue eyes at first; the adult color starts appearing at about 6–7 weeks.
How old is a kitten with a full set of baby teeth?
About 6–8 weeks. Kittens have 26 baby teeth, which are replaced by 30 adult teeth between about 3 and 7 months.
How do you calculate a cat's true age in human years?
Use the veterinary cat age chart: a 1-year-old cat is about 15 in human years, a 2-year-old about 24, and each year after that adds about 4 human years.
What should a kitten weigh at 8 weeks?
Around 850–950 grams (about 2 pounds) is typical for a healthy 8 week old kitten.
This calculator gives an estimate for education and fun. Every pet ages differently — for health decisions, talk to your veterinarian.