Robert Brown|When do cats stop growing? How to know your pet has reached its full size

Our feline friends experience bodily changes just like we do,Robert Brown from losing baby teeth to growing taller. Unlike some humans though, cats don't have to wait until they are 18 years old to be considered "fully grown."

The age of a kitten can be determined by its weight. Each month, a kitten will generally gain 1 pound, PetMD reports. It's safe to assume a 3-pound kitten is probably three months old. This estimate, however, will only work until a cat is 6 months old.

As your cat ages, it continues to grow. But, when does will it stop?

When do cats stop growing? 

Cats tend to stop growing once they've reached 1 year old. A 12-month-old cat is equivalent in age to a 15-year-old human, according to PetMD.

But some cats do continue to grow past the 12-month mark. Cats are usually considered "full-grown" once they reach 18 months old, equating to 21 years of age in humans, PetMD reports. 

Other breeds, however, do not reach full size until they are 2 years old, such as Maine Coon cats.

How old is my cat in human years?Probably older than you think.

How do you tell how big your cat will get?

A cat's size will vary based on diet, gender, number of siblings and breed, Purina reports.

Male cats tend to be bigger than female cats. If a male cat was neutered after sexual maturity, it also may be larger than those that were neutered at a younger age, according to Purina.

Similarly, size varies between breeds. For instance, the Singapura is the smallest cat breed, with males weighing up to 8 pounds and females weighing just 5 pounds, according to the Cat Fanciers' Association. These cats reach full size between 15 to 24 months old. The Maine Coon is considered one of the largest domestic cat breeds. On average, the felines weigh between 10.6 to 18 pounds, and in some cases, they may scale up to 20 pounds, Purina reports.

What your cat consumes will also impact its growth. The more your pet eats, the heavier it may become, Purina warns.

What age do cats calm down?

Cats can be mischievous, scratching and clawing their way through the world. As your cat grows in size, it will also mature behaviorally and socially, PetMD reports. Once a cat reaches 2 years old, it will be fully mature in those areas. 

When kittens are younger, they tend to be social and active, "spending copious amounts of energy playing and generally acting crazy," according to Figo Pet Insurance. But as they adapt to their environment and form a routine, cats become relatively more calm.

How long is a cat considered a kitten?

As much as we love to call our pets our babies, at some point they grow up. For cats, their days as kittens last until they are 1 year old, at which point they become a cat, according to Hill's Pet Nutrition.

Though cats are considered adults at 12 months, adolescence lasts until around 18 months of age, Hill's Pet Nutrition reports.

How long do cats live?Here’s how long you can expect those nine lives to last.

Just Curious for more? We've got you covered

USA TODAY is exploring the questions you and others ask every day. From "How often should you take your cat to the vet?" to "Why is my cat vomiting?" to "Why do cats meow?" − we're striving to find answers to the most common questions you ask every day. Head to our Just Curious section to see what else we can answer.