How does a cat's weight change with age? A cat grows fast in its first year, holds a steady weight through its adult years, and may lose weight — especially muscle — in its senior years. This guide is the cat weight by age chart: the expected weight at each life stage, by size, and how to use it for your own cat. Every figure is a range, not a prescription for an individual cat, and the right weight at any age is the one where the ribs are easy to feel, the waist is visible from above, and the cat moves well.
The short version is: a kitten should gain weight steadily, an adult should hold its weight steady, and a senior may lose weight slowly — but fast weight loss at any age needs a vet check. Weigh the cat monthly as an adult and every two weeks as a kitten, write the numbers down, and look at the line over months, not any single reading. The cat ideal weight calculator works out a target weight range, and the cat body condition score chart shows the nine-point scale vets use at every age.
Cat weight by age chart
The table below gives the typical adult weight, the senior age, and the typical lifespan for each size. The kitten years are covered in the growth section below, because a kitten's weight changes every few weeks and a single table row cannot capture it.
| Size | Typical adult weight | Senior from about | Typical lifespan |
|---|---|---|---|
| Small | 2–4 kg | About 11 years | 12 to 16 years |
| Medium | 3–6 kg | About 11 years | 12 to 16 years |
| Large | 5–11 kg | About 11 years | 10 to 14 years |
Read the table from left to right and the pattern is clear: weight follows size, and lifespan follows size in the other direction — smaller cats usually live longer than larger ones. The senior age follows the same pattern: a giant dog becomes a senior years before a toy dog does, and its senior years are shorter. That is why the senior boundary matters: it tells you when to start watching more closely, not when to stop enjoying your cat. The when is a cat considered a senior guide gives the thresholds in detail, and the how long do cats live guide gives the lifespans by size.
The kitten years: fast growth
A kitten grows fastest in the first few months, then slows down towards the end of its first year. 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. Weigh the kitten every two weeks, and look for a smooth, steady rise — not a flat line and not a sudden jump.
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. The kitten weight chart by age guide gives the full shares by age, and the how much food should a kitten eat guide gives the calorie tables for growing cats.
The adult years: holding steady
As an adult, a cat's weight should be stable: the same food, the same exercise, and the same weight, month after month. The adult years are when calorie mistakes show up most clearly, in one direction above all: weight gain. A cat that has stopped growing but keeps eating kitten amounts, or that becomes less active while its food stays the same, will put on weight a few hundred grams at a time until its ribs are hard to feel and its waist has gone. Weigh monthly, and if weight drifts up, cut food by about 10% and re-weigh in a month rather than changing everything at once.
Neutering is the biggest calorie change in the adult years: a cat that has been neutered typically needs about 10 to 20% fewer calories than before, and the weight gain that follows neutering is the main risk, not the operation itself. Cut food by roughly 10 to 20% after the operation and watch the waistline for the next few months. The cat weight gain after spaying guide covers the operation in detail, and the adult cat food calculator guide gives the calorie tables for the adult years.
The senior years: watching for loss
As a senior, a cat may lose weight — especially muscle — even when it is eating well, and that needs a vet check, not just more food. Senior cats lose weight for many reasons: dental pain, kidney disease, thyroid problems, diabetes, cancer, or simply the loss of muscle that comes with old age. A senior cat that is losing weight fast, or that has lost a lot of weight in a short time, needs a vet check promptly. Vet checks should move to twice a year from the senior boundary, with weight, teeth, and kidneys checked each time.
Feeding a senior cat is about holding muscle and weight steady, not about putting weight on fast: good protein in the food, gentle regular exercise every day, and food fed little and often. A senior cat that stops moving loses muscle fast and finds it hard to get it back, so keep it moving every day at a level that suits its body. The senior cat weight loss causes guide covers weight loss in older cats in full, and the senior cat diet guide covers the feeding plan for the senior years.
How to use the chart for your cat
Find your cat's size in the table, take the adult weight range as a starting point, and then check the cat with your hands at every age: ribs easy to feel under a thin layer of fat, waist visible from above, tummy tuck visible from the side. A kitten should be judged against its growth, not against the adult range — a kitten at half its expected adult weight at six months is growing well, even though it is far below the adult range. An adult should be judged against the range and the hands-on check together. A senior should be judged against its own past weights: a senior cat that has lost weight since last year needs a vet check, even if it is still inside its size's range.
Weigh monthly as an adult and every two weeks as a kitten, write the numbers down, and bring the record to the vet. A list of weights with dates is far more useful than a single number, because it shows the line over months — and the line is what tells the vet whether the cat is growing well, holding steady, or losing weight. The how to weigh your cat at home guide explains the bathroom-scale method, and the ideal cat weight chart by breed guide gives the typical ranges breed by breed.
For related reading, see the cat ideal weight calculator, the cat body condition score chart, the kitten weight chart by age guide, the when is a cat considered a senior guide, the senior cat weight loss causes guide, the how to weigh your cat at home guide.
Frequently asked questions
How does a cat's weight change with age?
A cat grows fast in its first year, holds a steady weight through its adult years, and may lose weight — especially muscle — in its senior years. A kitten should gain weight steadily, an adult should hold its weight steady, and a senior may lose weight slowly — but fast weight loss at any age needs a vet check.
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.
Should an adult cat's weight stay the same?
Yes — as an adult, a cat's weight should be stable, month after month. If weight drifts up, cut food by about 10% and re-weigh in a month. If weight drifts down without a change in food, mention it to your vet promptly — unexplained weight loss is always worth checking.
Why do senior cats lose weight?
Senior cats lose weight for many reasons: dental pain, kidney disease, thyroid problems, diabetes, cancer, or simply the loss of muscle that comes with old age. A senior cat that is losing weight needs a vet check, not just more food — and vet checks should move to twice a year from the senior boundary.
How often should I weigh my cat?
Monthly as an adult, and every two weeks as a kitten, because it grows fast. A pregnant or nursing cat should be weighed weekly, and a cat on a weight-loss or weight-gain plan should be weighed monthly so the plan can be adjusted.
When should I see a vet about my cat's weight?
See a vet if the cat is losing weight without a change in food, if it is losing weight fast, if it is a senior that is losing weight, if it is a young animal that is not growing, or if it is well outside its size's range. Bring the weight record and the food details.
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.