How Big Is A Cat? When Are Cats Full-Grown?

One day, you have a tiny kitten running around your house, and before you know it, they’re a big cat.

It may seem like they grow overnight, but cats actually go through five life stages, as explained by the American Association of Feline Practitioners and American Animal Hospital Association life stage guidelines.

One way to determine when your cat is full-grown is to see into which category they fall into:

• Kitten (birth to six months)
• Junior (six months to two years)
• Prime (three to six years)
• Mature (seven to 10 years)
• Senior and geriatric (11 years and up)

Much like their human counterparts, the development stages of kittens are counted in weeks and months up until the age of two. At what age are cats full-grown? At about one year old. Cats reach adulthood in the junior stage moving into prime stage. You can think of this as your cat being in their late teens and 20s, young adults full of energy and verve.

Once your cat ages into adulthood, your veterinarian can help you determine your cat’s ideal weight and recommend a meal plan to help optimize their health. You can work together to modify this plan as your cat moves into each new life stage. It’s important to schedule this visit so that these baselines can be established, allowing you to keep an eye on your cat’s wellness as they age.

How Do Gender and Breed Affect a Cat’s Size?

Studies suggest that there have been two lineages of cats. One lineage appeared in Asia Minor as early as 6,400 years ago, dispersing northward and westward into Europe. The other lineage appeared in Egypt between 6,400 and 1,000 years ago before spreading throughout the Mediterranean. Both lineages continued to breed with the African wildcat during their respective dispersals.

Once your cat is officially a grown-up, they reach their full size. A cat’s size is determined by their genetics: The average house cat weighs between six and 12 pounds and is about 18 inches long and 10 inches tall. A cat’s weight may fluctuate as they age, but physical traits such as size, as well as eye color, body length, coat pattern and texture, are fully developed by the age of two.

Generally speaking, male cats are larger than female cats in height, length and weight. This is common among mammals, reports Science Daily, and researchers chalk it up to natural selection.

How Do Breed, Gender, Neutering Status and Other Factors Affect Adult Cat Size?

The characteristics of the different cat breeds are well documented, but their size and dimensions are often not elaborated on. We have looked closely at several different breeds, collated data from various sources, and listed their average dimensions below.

While doing so, we’ll focus on domestic cat breeds. In other words, cats that are meant to live with people and would make a good lap cat or, at least, its size is suitable for a house cat.

Also, all dimensions mentioned in this article are for fully grown adult cats. You can consider your cat fully grown as of 18 months.

Males versus females

Looking at the different measurements like height, length and weight, the males are usually in the higher end of the range versus females being smaller and lighter, towards the lower end.

As a general rule, the average male cat size is about 1-3 inches (2.5-7.5cm) larger than female cats, and the average female cat’s weight is about 1 to 3 pounds lighter than their male counterparts.

Spaying and neutering

It was once believed that early neutering of cats (before seven months of age) would impact their growth negatively and that, as a result, neutered kittens (or puppies, for that matter) would be smaller than their un-neutered counterparts.

According to research done by several sources referenced here, early age neutering has no negative impact on a cat’s growth.

It may, however, slow down a cat’s metabolic rate, which, in turn, may cause them to gain weight.

Though some owners report that their cats gain weight after being fixed, this is not a result of the neutering itself but rather of the post-operative side effects. Cats tend to be lethargic for several weeks after surgery and may be hungrier during this time as well, leading to weight gain. Additionally, fixed cats need fewer calories than unfixed cats due to reduced hormonal activity, so they may put on a few pounds if their food portions aren’t adjusted.

Breed

Perhaps the biggest determining factor in a cat’s size is its breed. Some breeds can reach massive sizes, while others remain small even when fully grown. Most domestic cats are a mixture of different breeds and fall somewhere in between huge and tiny, but if your cat’s ancestry includes one of these breeds, it may be destined to reach greater (or lesser) heights.

Please note that the weights given are healthy ranges; as with all cats, these breeds can be overweight or underweight, so individual cats may weigh more or less than the amounts given here.

Big: Maine Coon

Clocking in at up to 25 pounds and measuring up to four feet in length, Maine Coons are truly massive cats. A Maine Coon holds the world record for the longest cat, and they’re comparable in size to wild Eurasian lynxes, which average about four feet long. Reaching such great sizes takes time; Maine Coons need three to five years to grow to their full adult size, compared to one year for most other breeds!

Big: Norwegian Forest Cat

Sometimes thought of as the European version of the Maine Coon, the Norwegian Forest Cat is a beast in its own right. Their big bones and fluffy coat contribute to their large sizes – up to 18 pounds for females and up to 20 for males.

Big: Bengal

Originally a cross between a domestic cat and an Asian Leopard, the Bengal sports the trademark spots of its wild ancestor in addition to its size and shape. Long, lean, and decidedly leopardlike, the Bengal can weigh up to 22 pounds. Combined with its highly active temperament, this large size makes it one of the trickiest breeds to keep.

Small: Singapura

With roots in Singapore, this breed has only been around since the 1970s, so it’s still fairly new to the cat world. Its large eyes and ears dwarf the rest of its body, which is around half the size of an average domestic cat. In fact, it barely weighs more than a kitten – fully grown females weigh around four pounds, while adult males tip the scales at six pounds.

Small: Munchkin

This breed is highly controversial, as its small size results from a genetic abnormality: dwarfism. Breeders intentionally select felines with this condition to produce cats with short legs (the signature feature of the Munchkin breed), but severe health conditions can appear later in the cat’s life, and some owners report that the Munchkin’s short legs prevent it from running and jumping. Though the Munchkin’s body is not much smaller than an average housecat’s, its legs are far shorter, reducing its weight to around six pounds for a female and eight pounds for a male.

Other factors affecting cat size

Several other factors can influence a kitten’s development. For example, poor hygiene will weaken the health of the mother and kittens, cause disease and impact growth, and a range of other health issues. Also, stress and fear when cats grow up in an abusive household can cause hormonal imbalance, disturbing growth.

How to Tell How Big Your Kitten Will Get

So how can you estimate the full-grown size of a kitten? Here are some tips:

• Know the breed: If you know the breed of kitten, you can estimate the average adult size based on breed standards. Purebred cats like Maine Coons and Bengals will be at the larger end of the spectrum.

• Look at the parents: The sizes of the mother and father cat provide clues to how big the kittens will get. If the parents are on the smaller or larger side, the kittens likely will be too.

• Consider gender: Male kittens tend to grow larger than females, so a male kitten may end up slightly bigger than a female littermate.

• Weigh often: Track your kitten’s weight weekly or monthly. Rapid early weight gains often (but not always) predict larger adult size.

• Healthy diet: Ensure your kitten gets proper nutrition to support healthy growth. Malnutrition can stunt growth.

• Check body condition: Kittens should appear lean but not too thin. Overweight kittens may grow into heavy adults.

While there are no guarantees, these tips can give you a general idea of the size range your kitten is likely to fall within when fully grown. Remember that every cat is an individual, so use breed averages as a guide, not an absolute. With proper care and nutrition, your kitten will reach the perfect size for them.

In Summary

• Cats reach full adult size around 1 year old
• Male cats tend to be bigger than females
• Spay/neuter status doesn’t affect size, but may impact weight
• Breed makes a big difference in adult size
• Factors like diet, exercise, and health influence size
• Know the parents’ size to estimate kitten growth
• With good nutrition, kittens reach their ideal mature size

No matter their final size, our feline friends bring joy, companionship, and endless entertainment. As long as your cat is healthy, their size is just one part of what makes them uniquely them! 😸