Three key factors determine how big your kitty will be.

By Kristi Valentini
October 15, 2020
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Emma Darvick

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. 

How Long Do Kittens Grow and When Do They Stop?

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). 

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,” reports Demos. 

How Can You 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. 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. 

Does Cat Breed Make a Difference?

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, says Demos, 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.

Does Gender Play a Role?

As with most species, male cats do run bigger than females. That means you can expect the average male cat’s weight to be closer to 14 pounds. “I would say male cats are usually 10 to 15 percent larger,” Demos says. “But you never know. I’ve met some really big female cats too.” 

Other Factors

According to Demos, one thing that makes a big difference in the growth of male kittens is neutering. Doing the procedure at an early age removes the stimulation of various hormones that are a part of the growing process. It abruptly stops the growth cycle. 

“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. 

“A common issue in male cats in the first half of their lives is the development of crystals in their urine,” reports Demos. “Those crystals can block the urethra and become a life-threatening emergency. If the urethra has a larger diameter, it decreases the risk of an obstruction.” 

Have a female cat? You don’t have to worry about the timing of spaying. The procedure doesn’t seem to impact females 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.