They won't stay small forever, and these key factors determine how big your kitty will be.
Three kittens at different ages
Credit: Corinne Mucha

Kittens, like other babies, grow up too fast. If we had our way, those adorable fluff balls would stay small forever (or at least a little longer). Wondering how long you have until your cat reaches adulthood? We talked with Lauren Demos, BVMS, Hons, DABVP (Feline), chief veterinary officer for Pettable and Top Vets Talk Pets correspondent, to find out when kittens stop growing and what you can expect along the way. 

When Do Cats Stop Growing?

You can expect your cat to be almost fully grown after a year. "For the average cat, 95 percent of growth is complete by nine to 12 months," Demos says. 

Most of a cat's growth happens in the first six months, Demos says. During this period, there's an exponential growth curve. Kittens are putting on a lot of weight, gaining muscle mass, and their bones are lengthening at a rapid rate. "Kittens can eat as much as they want at this stage because they need the nutrients to build proper bone and muscle structure," Demos says. 

Kittens do a lot of learning during this phase, too. It's a good time to expose your cat to experiences you want them to be open to in the future, like nail trimming and eating different types of foods (dry, wet, and shredded). 

How To Tell if Your Cat Is Fully Grown

Your cat should stop gaining weight when she's done growing. You can keep an eye on this with the following tip from Demos: Weigh your cat once or twice a month. In their first five months, most kittens gain about one pound per month. When your cat's weight reaches a plateau and is holding steady at 12 to 14 pounds—the healthy weight of an average domestic shorthair cat—that's a good indicator that your cat is fully grown. 

After reaching adulthood, cats continue to mature socially and behaviorally. Most of this development occurs in the first two years of a cat's life. Because kittens and younger cats are still learning and developing, it's the easiest time to bond and train.

Factors That Affect Kitten Growth

While age and weight are general cues to knowing your cat is fully grown, not all kittens are the same. Gender, breed, and neutering can each affect how long it takes your kitten to reach adulthood.


Some cat breeds are significantly smaller or larger than the average housecat. For example, Siamese, Sphynx, and Khao Manee cats generally have a lower body weight and may reach their full size earlier. Larger cat breeds like Maine coons can weigh up to 25 pounds or more. Their growth takes a minimum of two or three years, Demos says, because they're so much bigger than most other cat breeds. 

Ask your veterinarian what the average adult weight is for your cat's breed. That way, you'll know when your cat is reaching maturity and when to switch from kitten to adult food.


As with most species, male cats are typically bigger than females. That means you can expect the average male cat's weight to be closer to 14 pounds. "Male cats are usually 10- to 15-percent larger," Demos says. "But you never know. I've met some really big female cats, too." 


According to Demos, one thing that makes a big difference in the growth of male kittens is neutering. Neutering removes the stimulation of various hormones that are a part of the growing process. If the procedure is done too soon in a kitten's development, the growth cycle is stopped abruptly.

"If given a choice, I recommend waiting until your male kitten is closer to five or six months old before having the procedure," Demos says. The main reason for that is because the urethra—the tube that carries urine from the bladder to outside—will also grow larger if you don't neuter them too early in life. 

Have a female cat? You don't have to worry about the timing of spaying as the procedure doesn't seem to impact female cat's growth in the same way. 

Kittenhood is fleeting, so keep your camera at the ready. You'll want to capture your kitty's sweet baby face and silly antics. The good news: Although your cat will stop growing, her curiosity and zest for life (and naps) will always remain.