How Big Will My Cat Get Calculator

When you take a kitten home with you, questions inevitably arise. How big will it eventually be? This calculator offers solid estimates in three different ways.

You can predict the weight of an adult cat by using a kitten's current age and weight, researching typical size ranges for a breed, or estimating future weight based on parents' constitution. Please note that none of these predictions are absolutely accurate. Treat any result as a well-informed estimate rather than a guarantee.

How big will my cat be?

Most cats reach their adult weight by the age of ten to twelve months. The typical domestic cat usually weighs about eight to twelve pounds.

The size range varies widely by breed. While a Singapura may top out at about 5 pounds, Maine Coons can reach over 20 pounds. The most reliable method for predicting the growth of any particular kitten is to track its weight over time, as the growth curve in kittens is generally fairly consistent.

Here's how to use this calculator.

Please select the method that best fits with the information you have available.

For growing kittens, the method that takes into account age and current weight is most accurate. When you input the kitten's age and current weight, a calculator will multiply this weight by a growth factor to estimate adult weight.

For purebred cats or if you are certain of the breed, the method that takes into account breed and sex is useful. It shows the typical weight range for adult cats based on the breed standard and refines this range according to sex. If you know how big the mother and father cat became, then a method that takes into account the parents' body size can also be used. This is because kittens usually grow up to a weight between their parent's weights.

Growth factors for kittens

The age-based method is based on a simple idea: At each stage of development, the weight of a kitten corresponds to a known percentage of its eventual adult weight. So you can multiply the current weight by the appropriate growth factor to estimate the adult weight.

At sixteen weeks of age the factor is about 2. This is the basis for a well-known rule of thumb: double the weight of a four-month-old kitten to get an estimate of adult weight.

We are assuming a kitten that weighs four pounds at sixteen weeks of age. Multiplying this by two gives an estimated adult size of about eight pounds. Allowing for normal variations, the range is likely to be between 6.4 and 9.6 pounds.

The younger the kitten is, the larger this factor will be as it still has to grow. As the kitten gets older and closer to its final weight, the estimated range narrows down.

When do cats stop growing?

Most cats are fully grown by the time they're ten to twelve months old, and will have reached about three-quarters of their adult weight by six months. The subsequent increase in weight is very small.

The exceptions are larger breeds that take longer to mature. Maine Coons, Ragdolls, Norwegian Forest Cats and Siberian cats continue growing after their first birthday, sometimes up until the age of three or five years old. As this method assumes cats reach maturity around one year old, you should consider these breeds' stated values as a minimum, in addition to breed information.

What factors affect a cat's body weight?

Breed and genetic factors determine the upper limit. Breed itself explains most of the differences in adult cat size, and within a breed kittens tend to develop a size similar to that of their same-sex parents.

Sex is another important factor. Male cats of a particular breed are usually about 15 to 20 percent heavier than female cats, with the difference being greatest in large breeds.

Diet determines whether a cat will reach its genetic growth potential. If a cat is underfed during the growth phase it may be smaller than it should be. On the other hand overfeeding does not result in a larger skeleton, but rather obesity. While castration or sterilization has little effect on final skeletal size, it can affect propensity for fat deposition, so careful control of food intake after surgery is important.

How big will my Maine coon be?

Maine Coons usually weigh between 15 and 25 pounds, while females can weigh from 10 to 15 pounds. The body length from nose to tail can be almost 40 inches long.

Because they mature so slowly, Maine Coon kittens often look completely normal even when they are four months old but will continue to grow for several more years. The use of this calculation for a particular breed takes into account their longer growth period.

Can you predict a cat's eventual size by its paw?

Big feet are only a rough guide and not an accurate measurement. Kittens with big skeletons often have wider paws and tend to grow into larger cats. However, there is individual variation in foot size that can be so great as to make this method less reliable than tracking weight over time.

For more accurate estimates:

Weigh the kitten every one to two weeks with the same scale and look at the trend rather than individual measurements. Adjust your estimate over time as it gets older. The closer a kitten is to adulthood, the tighter the prediction range will be.

If your kitten's weight is significantly below or above the healthy range for their age, or if they are not gaining weight or losing it, consult a veterinarian.

This calculator is for general information purposes only and does not constitute veterinary advice. As every cat is different, a vet can assess the growth and health of your pet. The results are not intended to be diagnostic but serve as a starting point.