How Do I Know When My Puppy Is Fully Grown?

In this article:   

• How long do puppies grow?
• When should I spay or neuter my puppy?
• When do growth plates close in puppies?
• What should I feed a growing puppy?
• How do I know when my puppy is done growing?

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This article was originally published in June of 2023, and has been updated.

In the children’s book Clifford the Big Red Dog, a girl named Emily Elizabeth nurtures the title dog, initially the runt of his litter, until he stands 8 to 35 feet tall. Real-life dogs don’t reach these proportions—but you may be curious just how big yours will get, and when they’ll reach that full size.

Dogs don’t come with a handy readout letting you know they’re done growing, but there are some tells. “They’ll start to lose some of those puppy characteristics,” said Kaitlyn Krebs, DVM, Diplomate of the American Board of Veterinary Practitioners (canine/feline), clinical professor of primary care at Rowan University’s Shreiber School of Veterinary Medicine. Their downy-soft fur will thicken, their puppy teeth will fall out, and, as Dr. Krebs told us, “they’ll stop being so floppy.” If you’ve seen a few puppies, you know what she means.

Genetics (including breed), diet, spay/neuter status, and more dictate exactly when a particular dog will reach their full size. Here’s how to tell when your puppy is due to reach that milestone.

How long do puppies grow?

Puppies grow for anywhere from eight to 24 months, with their skeletons fully maturing between two and eight months after they’ve finished growing. 

“If you look at the miniature toy breeds, they actually don’t grow much after they’re 4 or 5 months of age, reaching skeletal maturity around 6 or 7 months,” said Scott Rutherford, Diplomate and Fellow of the European College of Veterinary Surgeons, Certificate in Small Animal Surgery and assistant professor at The Ohio State University College of Veterinary Medicine. “Whereas our giant dogs—the Saint Bernards and Great Danes—they’ll be growing until they’re 10 or 11 months of age, and then actually don’t reach skeletal maturity until about 18 months.”

Here’s how growth periods break down by breed size, according to Dr. Krebs. Note that how long a puppy grows depends on whether they’re spayed or neutered:

• Small (20 pounds or less fully grown): Fully grown between 8 and 12 months
• Medium (20 to 50 pounds fully grown): Fully grown between 10 and 15 months
• Large (50 to 100 pounds fully grown): Fully grown between 12 and 18 months
• Giant (100 pounds or more fully grown): Fully grown between 18 and 24 months

In general, smaller dogs finish growing sooner and larger dogs finish later. A mixed-breed puppy’s growth is less predictable (and at-home DNA tests aren’t always accurate).

Talk to your vet about when you can expect your pup to reach their full size—this conversation can inform how and when you choose to feed, exercise, and spay or neuter them.

When should I spay or neuter my puppy?

Different vets have different opinions on the best time to spay or neuter a puppy, but they agree that reproductive hormones impact dogs’ growth. 

As puppies approach sexual maturity, testes in males release testosterone and ovaries in females release estrogen, both of which contribute to musculoskeletal growth. 

“From a purely orthopedic point of view, it would be ideal if you could wait until skeletal maturity,” said Dr. Rutherford.

“We like them to get some of that hormonal influence until they’re fully grown so those hormones can help them fully develop,” said Dr. Krebs. Size factors in, she added; smaller dogs can be spayed or neutered younger while large or giant dogs, who are at higher risk of orthopedic disease, ought to wait until they’re a year and a half to 2 years old. In Bernese Mountain dogs, German shepherds, golden retrievers, Labs, Rottweilers, and St. Bernards, for example, early neutering increases the risk of joint disorders, Dr. Rutherford said.

Some research, like this 2024 paper, indicates that spaying or neutering a puppy too early increases their risk of certain cancers and orthopedic diseases, depending on the breed. However, Dr. Rutherford said, the quality of evidence varies, so the question of precisely how spaying and neutering affects a puppy’s growth is a “controversial topic.”

In addition to preventing unwanted pregnancy, neutering or spaying  decreases the risk of other cancers, especially mammary and ovarian cancer. In intact females, every heat cycle increases their risk of mammary cancer, according to the Animal Humane Society. Intact males are more prone to prostate and testicular conditions, including testicular cancer.

Ultimately, “there are advantages and disadvantages both ways,” Dr. Rutherford said. “There is no right or wrong answer here.” Talk to your veterinarian about the best time to spay or neuter your dog.

When do growth plates close in puppies?

A puppy’s bones lengthen as they reach their full size, and then solidify. This process can take anywhere from one to two years.

“A lot of the bone growth happens at the end of the bones,” said Dr. Rutherford. In particular, the long bones in the front and back legs have regions called physes, or growth plates, on either end. Growth plates are made of cartilage cells, which replicate and grow. “About 75% of the length of bone is done at the growth plates,” Dr. Rutherford said.

These plates grow the most when a puppy is very young. “In most dogs, skeletal growth has largely ceased by 10 months of age with the most rapid elongation very early in life—between 10 and 14 weeks of age,” said Derek Fox, DVM, PhD, Diplomate of the American College of Veterinary Surgeons, a professor of small animal orthopedic surgery at the University of Missouri’s Veterinary Health Center.

Once bones finish growing, they continue to mature until they’re fully ossified, or hardened into solid bone. Typically, growth plates close “a few months” after they finish growing, Dr. Rutherford said. Growth plates typically fuse during late puberty because of sexual reproduction hormones circulating in the blood, according to Dr. Fox.

But dogs spayed or neutered at 7 months or younger “experience a significant delay” in closure of these growth plates, Dr. Fox said. These plates aren’t necessarily still growing, but they take longer to ossify. 

What should I feed a growing puppy?

Puppies require appropriate nutrition to support their rapid growth. Feed them a complete and balanced diet formulated for growth and reproduction, or for all life stages; puppies require more energy and nutrients from their diet than adults do, and properly formulated food fulfills these needs.

The Farmer’s Dog offers recipes suitable for dogs at every stage of life, including large-breed puppies. Our Customer Care team will work with you as your puppy grows to ensure they’re getting all the essential vitamins and nutrients they need for healthy development.

How do I know when my puppy is done growing?

A puppy is done growing when their growth plates have fully hardened. You can’t tell just by looking at your dog when that’s happened—but some other cues signal that they’re fully grown, or approaching that stage.

“Up to 10 months of age, certain parts of the body may seem out of proportion—like disproportionately large paws,” said Dr. Fox. “But at 10 to 11 months of age, proportionality is normalized depending on breed.” He added that this is a critical time to prevent overfeeding in large- and giant-breed dogs so they don’t become overweight, which increases the risk of orthopedic conditions like osteoarthritis and hip dysplasia.

You can also measure their height, from their front paws to the top of their head. “Once they’ve stopped growing taller, that’s usually when we can say they’re probably finished growing, even if they continue to gain weight,” Dr. Krebs said. You can measure and record your puppy’s height weekly to track their growth trends. Puppies tend to grow most rapidly when they’re very young, and “closer to maturity, the gains will be a little bit smaller,” Dr. Krebs said. Once they’re at a consistent height with no changes between measurements, they’ve reached their full size—but may continue to gain weight, as Dr. Krebs said.

Ask your vet about your puppy’s growth if you’re not sure whether they’ll continue to get bigger as they transition to adulthood.

Knowing what to expect will help you support them as they change from a floppy little puppy into a healthy, hearty dog who’s less than 35 feet tall, but bigger than they are right now.

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