What should a kitten weigh at each age? A kitten grows fast, and its weight changes every few weeks — so the answer is not a single number, but a chart: the expected weight at each age, as a share of the kitten's expected adult weight. This guide is that chart in words, plus how to use it, how to weigh a kitten, and when a kitten that is off the chart needs a vet. Every figure is a very rough guide, because individual cats vary widely, and the chart is a starting point for a conversation with your vet — not a verdict on your kitten.
The short version is: weigh the kitten every two weeks, compare with the breed's expected adult weight, and look for a smooth, steady rise — not a flat line and not a sudden jump. As a very rough guide, a kitten's weight as a share of its expected adult weight is about a fifth to a quarter at 8 weeks, about a quarter to a third at 3 months, about a third to two-fifths at 4 months, about half to two-thirds at 6 months, about three-quarters to four-fifths at 9 months, and about four-fifths or more at 12 months, when small breeds are near-adult and large breeds are still growing. The kitten weight predictor estimates adult weight from the kitten's current weight and age, and the kitten weight calculator by breed size guide explains how to track growth against the breed's expected adult weight.
Kitten weight chart by age
The table below gives the expected adult weight by size, and the very rough weight at 8 weeks and at 6 months for each size. The 8-week and 6-month figures are rough shares of the adult weight, not measurements from a study of individual breeds — use them to check whether your kitten is broadly on track, not to judge it to the gram.
| Size | Expected adult weight | Weight at 8 weeks (very rough) | Weight at 6 months (very rough) |
|---|---|---|---|
| Small | 2–4 kg | About 1–1 kg at 8 weeks (very rough) | About 1–2 kg at 6 months (very rough) |
| Medium | 3–6 kg | About 1–2 kg at 8 weeks (very rough) | About 2–4 kg at 6 months (very rough) |
| Large | 5–11 kg | About 2–3 kg at 8 weeks (very rough) | About 3–7 kg at 6 months (very rough) |
Read the table from left to right and the pattern is clear: a kitten grows fastest in the first few months, then slows down towards the end of its first year, and large breeds keep growing long after small breeds have finished. A kitten that is well outside the rough share for its age — much heavier or much lighter than the table suggests — should be checked by a vet, rather than having its food changed on your own.
How a kitten's weight changes as it grows
A kitten does not grow evenly: it grows fastest in the first few months, then slows down towards the end of its first year. In the first weeks, a kitten should gain weight every day — a newborn kitten that is not gaining weight needs a vet check, not just more food. By 8 weeks, a kitten is about a fifth to a quarter of its expected adult weight. By 3 months it is about a quarter to a third, by 4 months about a third to two-fifths, by 6 months about half to two-thirds, by 9 months about three-quarters to four-fifths, and by 12 months about four-fifths or more, when small breeds are near-adult and large breeds are still growing.
Those shares are very rough, and individual cats vary widely — a kitten that is a little above or below the share for its age is usually fine, as long as it is gaining weight steadily and is bright, eating, and active. What matters is the line over weeks: a smooth, steady rise. A kitten that is not gaining weight at all over two weeks, or that is losing weight, needs a vet check. A kitten that is gaining weight in sudden jumps may be overfed, and a kitten that is gaining weight very slowly may be underfed or unwell — either way, the vet is the right next step, not a change in food on your own.
How to weigh a kitten and track its growth
Weigh the kitten every two weeks, at the same time of day, on the same scales, and write the number down — the line over weeks is what matters, not any single reading. For a small kitten, step on the bathroom scales holding it, then step on without it, and take the difference. For a larger puppy, use the vet's scales at a routine visit. Plot the weights on a simple chart, or just keep a list with dates: what you are looking for is a smooth, steady rise, not a flat line and not a sudden jump.
Feel the ribs at every weigh-in: you should feel them easily under a thin layer of fat, and see a waist from above and from the side, even in a kitten. A kitten that is too fat is not a healthy kitten: excess weight in youth sets up weight problems for life, and in a large-breed puppy it strains developing joints. A kitten that is too thin is not a healthy kitten either: it may not be getting enough food, or it may be unwell. The table above gives the rough shares; the scales and your hands tell you whether the kitten is on track. The how much food should a kitten eat per day by weight guide gives the calorie tables by weight, and the how often should you feed a kitten guide gives the feeding schedule.
When a kitten's weight needs a vet
See a vet promptly if the kitten is not gaining weight over two weeks, if it is losing weight, if it is much heavier or much lighter than the rough share for its age, if it is lethargic or off its food, or if it has vomiting or diarrhoea. A kitten that is not growing needs a vet, not just more food — parasites, infections, and other problems can all slow growth, and they need treating. Bring the weight record: a list of weights with dates is far more useful to a vet than a single number, because it shows the line over weeks.
At the vet, expect a weigh-in, a check of the kitten's body condition, and questions about food, feeding times, and other pets in the house — and possibly a stool sample, because parasites are a common cause of slow growth in young animals and are easy to treat. Do not try to make a kitten grow faster with extra food: rapid growth and excess weight strain developing joints, and in a large-breed puppy that matters more than in a small one. The kitten too skinny — what to do guide covers a kitten that is too thin, and the how much should a kitten eat guide gives the calorie tables.
Common mistakes with kitten weight
The most common mistake is weighing too rarely: a kitten grows fast, and a kitten weighed once a month is already being weighed too rarely — weigh every two weeks. The second is judging by a single reading: a kitten that is a little above or below the chart on one day is usually fine, and the line over weeks is what matters. The third is overfeeding to make the kitten grow faster: rapid growth and excess weight strain developing joints, and in a large-breed puppy that matters more than in a small one. The fourth is underfeeding a kitten that is growing fast, because the owner is afraid of overfeeding: a kitten that is not gaining weight needs a vet check, not a smaller portion.
The fifth is comparing kittens of different breeds or sizes: a large-breed puppy at 6 months weighs far more than a small-breed puppy of the same age, and both are normal for their size. Compare your kitten with its own breed's expected adult weight, not with another kitten of a different size. The kitten growth chart by breed size guide gives the growth tables by size, and the when is a cat fully grown guide gives the growth ages by size and breed.
For related reading, see the kitten weight predictor, the kitten weight calculator by breed size guide, the how much food should a kitten eat guide, the how often should you feed a kitten guide, the kitten too skinny — what to do guide, the when is a cat fully grown guide.
Frequently asked questions
How much should a kitten weigh at 8 weeks?
As a very rough guide, about a fifth to a quarter of its expected adult weight. A kitten that will be 10 kg as an adult is roughly 2 to 2.5 kg at 8 weeks, and a kitten that will be 30 kg as an adult is roughly 6 to 7.5 kg. Those are rough shares, not measurements — individual cats vary widely, and the line over weeks matters more than any single reading.
How much should a kitten weigh at 6 months?
As a very rough guide, about half to two-thirds of its expected adult weight. A kitten that will be 10 kg as an adult is roughly 5 to 6.5 kg at 6 months, and a kitten that will be 30 kg as an adult is roughly 15 to 20 kg. Small breeds are nearer adult at 6 months than large breeds, which keep growing for longer.
How often should I weigh my kitten?
Every two weeks, at the same time of day, on the same scales, and write the number down. A kitten grows fast, and the amount of food changes quickly, so a kitten weighed once a month is being weighed too rarely. Plot the weights on a simple chart, or keep a list with dates.
My kitten is not gaining weight — what should I do?
See a vet promptly. A kitten that is not gaining weight over two weeks, or that is losing weight, needs a vet check — parasites, infections, and other problems can all slow growth, and they need treating. Do not just feed more: a kitten that is not growing needs a vet, not just more food.
Can a kitten be overweight?
Yes — a kitten that is too fat is not a healthy kitten. Excess weight in youth sets up weight problems for life, and in a large-breed puppy it strains developing joints. Feel the ribs at every weigh-in: you should feel them easily under a thin layer of fat, and see a waist from above and from the side, even in a kitten.
When is a kitten fully grown?
Small breeds finish growing at about 9 to 12 months, medium breeds at about 12 months, large breeds at about 12 to 18 months, and giant breeds at 18 months to 2 years. For cats, most breeds finish at about 12 months, but large breeds such as the Maine Coon can keep growing until 2 to 4 years.
Results on this page are estimates for general information only and are not veterinary advice. If your pet is ill, underweight, overweight, pregnant, or has a health condition, consult your veterinarian before changing diet or care.