Project your kitten's adult weight from its breed, age, and current weight — with breed growth curves, a weigh-in tracker, and a mixed-breed estimator. Free, private, and runs entirely in your browser.
Educational estimate — not veterinary advice. Growth projections are based on breed averages; individual cats vary a lot. Always confirm health or feeding decisions with your veterinarian.
Units:
Don't know the breed? Choose "Domestic Shorthair / Longhair (mixed)".
Sex
Tip: 8 weeks = 2 months.
Projected adult weight
– kg
Educational estimate — not veterinary advice. Individual variation is large; neutered or overfed cats may land heavier.
Log weigh-ins over time and compare them against your kitten's expected breed curve. Data stays in this browser only (localStorage) — nothing is uploaded.
Sex
Date
Age
Weight
vs expected
Option A — you know the parents' adult weights
Kitten's sex
Estimated adult weight (mid-parent method)
– kg
Educational estimate — not veterinary advice.
Option B — the paw-size test for fun only
Old folklore says big paws mean a big cat. There is no science behind this — paw size does not predict adult weight. The result below is entertainment, not an estimate.
"Fun" estimate — no scientific basis
–
What this tool does — and doesn't — do
This calculator projects a growing kitten's future adult weight. It is different from our sibling cat tools:
Cat BMI calculator — checks whether your cat's current weight is healthy. Present, not future.
Cat calorie calculator — works out daily food portions from current weight. Feeding, not growth.
Cat growth chart by breed: adult weight ranges
Typical healthy adult weight ranges compiled from CFA/TICA breed profiles, PetMD, and VCA breed pages. "Fully grown by" is the age skeletal growth is normally complete; large breeds may keep filling out into year three.
Breed
Size
Adult male
Adult female
Fully grown by
Maine Coon
Large
5.9–8.2 kg (13–18 lb)
3.6–5.4 kg (8–12 lb)
24 months
Ragdoll
Large
5.4–9.1 kg (12–20 lb)
3.6–6.8 kg (8–15 lb)
24 months
Norwegian Forest Cat
Large
4.5–9.0 kg (10–20 lb)
3.5–5.5 kg (8–12 lb)
24 months
Siberian
Large
5.4–9.0 kg (12–20 lb)
3.6–6.8 kg (8–15 lb)
24 months
Savannah
Large
5.4–11.3 kg (12–25 lb)
4.5–8.0 kg (10–18 lb)
20 months
British Shorthair
Medium
4.1–7.7 kg (9–17 lb)
3.2–6.4 kg (7–14 lb)
18 months
Bengal
Medium
4.5–6.8 kg (10–15 lb)
3.6–5.4 kg (8–12 lb)
18 months
American Shorthair
Medium
3.4–6.8 kg (7–15 lb)
3.2–5.4 kg (7–12 lb)
18 months
Persian
Medium
3.6–7.0 kg (8–15 lb)
2.7–5.4 kg (6–12 lb)
18 months
Birman
Medium
4.5–6.8 kg (10–15 lb)
2.7–4.5 kg (6–10 lb)
18 months
Turkish Van
Large
3.6–8.2 kg (8–18 lb)
2.7–5.4 kg (6–12 lb)
18 months
Chartreux
Medium
4.5–7.3 kg (10–16 lb)
2.7–4.5 kg (6–10 lb)
18 months
Ocicat
Medium
3.6–6.8 kg (8–15 lb)
2.7–4.5 kg (6–10 lb)
18 months
Nebelung
Medium
3.2–7.3 kg (7–16 lb)
2.7–4.5 kg (6–10 lb)
18 months
Siamese
Medium
3.6–5.4 kg (8–12 lb)
2.7–4.5 kg (6–10 lb)
12 months
Abyssinian
Medium
3.6–5.0 kg (8–11 lb)
2.7–4.0 kg (6–9 lb)
12 months
Russian Blue
Medium
3.6–6.8 kg (8–15 lb)
2.7–4.5 kg (6–10 lb)
12 months
Sphynx
Medium
3.6–5.4 kg (8–12 lb)
2.7–4.0 kg (6–9 lb)
12 months
Scottish Fold
Medium
3.6–6.0 kg (8–13 lb)
2.7–5.4 kg (6–12 lb)
12 months
Burmese
Small
3.6–5.4 kg (8–12 lb)
2.7–4.0 kg (6–9 lb)
12 months
Oriental
Small
2.7–5.4 kg (6–12 lb)
2.3–4.5 kg (5–10 lb)
12 months
Turkish Angora
Small
3.2–5.0 kg (7–11 lb)
2.7–4.5 kg (6–10 lb)
12 months
Balinese
Small
2.7–4.5 kg (6–10 lb)
2.3–3.6 kg (5–8 lb)
12 months
Bombay
Small
3.6–5.0 kg (8–11 lb)
2.7–3.6 kg (6–8 lb)
12 months
Cornish Rex
Small
2.7–4.5 kg (6–10 lb)
2.3–3.6 kg (5–8 lb)
12 months
Devon Rex
Small
2.7–4.5 kg (6–10 lb)
2.3–3.6 kg (5–8 lb)
12 months
Singapura
Small
2.7–3.6 kg (6–8 lb)
1.8–2.7 kg (4–6 lb)
12 months
Munchkin
Small
2.7–4.1 kg (6–9 lb)
2.3–3.6 kg (5–8 lb)
12 months
Egyptian Mau
Medium
3.6–5.4 kg (8–12 lb)
2.7–4.0 kg (6–9 lb)
12 months
Domestic Shorthair / Longhair (mixed)
Medium
3.6–5.4 kg (8–12 lb)
2.7–4.5 kg (6–10 lb)
14 months
When do cats stop growing?
It depends on size class:
Small & medium breeds (Siamese, Russian Blue, Devon Rex, Singapura…): full size around 12 months.
Medium-large breeds (British Shorthair, Bengal, Persian, American Shorthair…): full size around 18 months.
Giant, slow-maturing breeds (Maine Coon, Ragdoll, Norwegian Forest Cat, Siberian, Savannah): keep growing until 20–24 months, and their frame can keep developing into year three.
Note the difference between frame and weight: the skeleton is usually done first, then the cat "fills out" with muscle for several more months. Weight gained after the frame is finished is usually fat, not growth.
Average kitten weight by month
A rough month-by-month guide for an average domestic kitten (large breeds run heavier, small breeds lighter):
Age
Typical weight
What's happening
Birth
0.1 kg (3–4 oz)
Eyes closed; should double birth weight in ~2 weeks
1 month
0.45 kg (1 lb)
Eyes open; starting to walk
2 months
0.9 kg (2 lb)
Weaning; first vaccines
3 months
1.4 kg (3 lb)
Socialization peak
4 months
1.9 kg (4 lb)
Fastest growth phase
5 months
2.3 kg (5 lb)
Losing baby teeth
6 months
2.8 kg (6 lb)
~60–70% of adult weight
8 months
3.4 kg
Growth visibly slowing
10 months
3.8 kg
Nearly full frame
12 months
4.3 kg
Adult size for most breeds
How the projection works (methodology)
The calculator divides your kitten's current weight by the fraction of adult weight a typical kitten of that breed has reached at its age:
Standard curve (breeds maturing by 18 months): ~19% at 2 months, 42% at 4 months, 62% at 6 months, 80%+ at 12 months, 100% by 18 months.
Slow curve (Maine Coon, Ragdoll, Norwegian Forest Cat, Siberian, Savannah — maturing at 20–24 months): ~25% at 3 months, 56% at 6 months, 80% at 12 months, 94% at 18 months, 100% by 24 months.
The "on track / above / below" badge compares current weight against the breed's expected weight for that age (breed midpoint × curve fraction), with a ±15% tolerance band.
Honest limitations
Individual variation is large — runts, large litters, and plain genetics move cats well outside breed ranges.
Neutering slows metabolism ~20–30%; neutered cats often land heavier if portions aren't adjusted.
Overfeeding makes kittens fatter, not larger-framed.
Parent weights for mixed-breed estimates are often guesses; treat that mode as a rough range.
This is an educational estimate — not veterinary advice, and never a substitute for a vet exam.
🔒 Privacy: everything runs in your browser. Your cat's data never leaves this page — no account, no tracking of inputs, no server.
Frequently asked questions
How accurate is this cat size calculator?
It is an educational estimate, not a prediction. The projection divides your kitten's current weight by the fraction of adult weight a typical kitten of that breed has reached at that age. Breed averages hide huge individual variation: litter size, birth weight, nutrition, neutering, and plain genetics can move a cat well outside the breed range. Treat the number as a starting point for a conversation with your veterinarian, not a guarantee.
How big will my kitten get?
Pick your kitten's breed (or Domestic Shorthair/Longhair for a mixed-breed cat), enter its sex, age, and current weight, and the calculator projects its adult weight from the breed's growth curve. As a rough rule of thumb, most kittens weigh about 1 lb (0.45 kg) per month of age for the first 4-5 months, reach about 60-70% of adult weight by 6 months, and are nearly full size by 12 months.
When do cats stop growing?
Most domestic cats reach their full skeletal size around 12 months and keep filling out until about 14-18 months. Slow-maturing large breeds are the exception: Maine Coons, Ragdolls, Norwegian Forest Cats, and Siberians keep growing until 18-24 months and may not reach their full frame until age 3-4. This calculator uses a slower growth curve for those breeds and the standard curve for everything else.
Can you tell how big a cat will get from its paws?
No, and this is worth saying plainly: there is no scientific evidence linking paw size to adult body size in cats. Unlike some old dog folklore, a kitten with big paws is not guaranteed to become a big cat. This tool includes a paw-size option only as a bit of fun, clearly labeled as folklore, and it should never be used to make feeding or health decisions.
Do male cats get bigger than females?
Yes, in almost every breed males are noticeably larger than females, often by 20-40%. That is why this calculator asks for your cat's sex and uses separate adult weight ranges for males and females. A female Maine Coon at 4.5 kg can be perfectly on track while a male of the same age at the same weight would be below his breed curve.
What is the Maine Coon growth chart?
Maine Coons are the classic slow growers. A rough month-by-month guide for a male: about 2 kg at 3 months, 4-5 kg at 6 months, 5.5-7 kg at 12 months, and 7-9 kg at full maturity around 2 years. Females run roughly 60-70% of those numbers. Because they mature so slowly, a 6-month-old Maine Coon is only a little over half its adult weight, which is why breed-specific curves matter.
My kitten is smaller or bigger than the breed chart. Is that normal?
Often, yes. Runts of the litter, kittens from large litters, and early weaning can all produce a kitten that sits below the curve but grows into a healthy adult. Being above the curve is more often about body condition than frame size. What matters most is steady growth along the kitten's own curve and a healthy body condition. If your kitten stops gaining, loses weight, or looks very thin or round, ask your veterinarian rather than the internet.
Does neutering or spaying make cats bigger?
Neutering does not make a cat's skeleton bigger, but it slows metabolism by roughly 20-30% and often increases appetite, so neutered cats gain fat more easily if portions are not adjusted. Growth plates also close slightly later in neutered kittens. The practical takeaway: weigh food, do not free-feed endlessly, and track weight with the growth tracker on this page.
How much should my kitten weigh by month?
For an average domestic kitten, very roughly: 0.1 kg at birth, 0.45 kg at 1 month, 0.9 kg at 2 months, 1.4 kg at 3 months, 1.9 kg at 4 months, 2.3 kg at 5 months, 2.8 kg at 6 months, 3.4 kg at 8 months, 3.8 kg at 10 months, and 4.3 kg at 12 months. Large breeds run heavier and small breeds lighter at every step, which is why the breed table on this page exists.
How big will my mixed breed cat get?
Use the Mixed Breed tab. If you know both parents' adult weights, the calculator averages them and adjusts slightly by the kitten's sex (males trend toward the father's end of the range, females toward the mother's). If the parents are unknown, the honest answer is the domestic average: most mixed-breed males land between 3.6-5.4 kg and females between 2.7-4.5 kg.
At what age is a cat fully grown in weight versus frame?
Frame (skeleton and length) is mostly done by 12 months for standard breeds, but weight keeps creeping up as the cat fills out with muscle until about 14-18 months. After that, further weight gain is usually fat, not growth. That is exactly why the growth tracker compares weigh-ins against the expected curve: it helps you spot the difference between healthy filling-out and creeping overweight.
Why is my cat still growing at 2 years old?
If it is a Maine Coon, Ragdoll, Norwegian Forest Cat, Siberian, or Savannah, that is completely normal: these breeds mature at 20-24 months and their frames can keep developing into year three. For any other breed, real skeletal growth past 18 months is unusual, and continued weight gain is more likely extra body fat worth discussing with your vet.
Does overfeeding make a kitten grow bigger?
No. Overfeeding a kitten makes it fatter, not larger-framed; adult skeletal size is set mostly by genetics. Excess weight in kittens raises the risk of obesity for life, because fat cells created early tend to stick around. Feed for steady, moderate growth along the curve, not maximum speed.
What are the kitten growth stages?
Neonatal (0-2 weeks): eyes closed, doubling birth weight. Transitional (2-4 weeks): eyes open, first wobbly steps. Socialization (4-12 weeks): weaning, rapid learning, first vaccines. Juvenile (3-6 months): losing baby teeth, huge energy, fastest growth. Adolescent (6-12+ months): growth slows, sexual maturity arrives, and for large breeds the slow road to full size continues into year two.
Is this the same as the cat age calculator?
No. Our cat age calculator (catculator) converts a cat's age into human-equivalent years; this tool projects how much a growing kitten will weigh as an adult. Related but different: our cat BMI tool checks whether your cat's current weight is healthy, and our cat calorie calculator works out daily food portions. Each answers one question well.
Should I ask my vet about my kitten's growth?
Yes, especially at vaccination visits. Bring your weigh-in history from the growth tracker: a vet can tell in seconds whether a kitten is tracking normally or needs attention. This page is an educational estimate, not veterinary advice, and it never replaces a hands-on exam.
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