When are Dogs Full Grown?


Dogs age seven years to every one human year – or so we’ve been told. In reality, the way dogs age is complex and not so easily figured out.

Despite the uncertainty behind where the seven-to-one ratio came from, veterinarians now agree that this isn’t the most accurate form of deciding a dog’s age.

Recent studies have changed that ratio, taking into account the size of the dog breed as well as other physical changes which happen in the first year of a dog’s life.

when are small dogs full grown

Big and small dogs definitely live shorter lifespans than humans, but how does it work?

At what age is a dog middle-aged, and when should we as owners start worrying about the maladies that come with old age?

Puppy Years: Fast-Paced Childhood

According to the American Kennel Club, dogs grow rapidly in the first few years of their life.

No matter the breed, those developmental years are where the most changes happen, meaning that one year to us feels like many more to the canines.

Their bodies shift and mold by tremendous degrees, though it’s apparent that bigger dog breeds change even faster than their smaller counterparts.

They develop the same way we do as children – growing tall, filling out, and solidifying bones into place. So, seven years rolled into one doesn’t seem so wrong, right?

But vets now concur that at the end of that first year, dogs have gone through as many changes as a fifteen year old person.

After their first 12 months of life, dogs are teenagers; mostly full-grown but not fully there, neither mentally nor physically.

As such, it’s recommended that dog owners be careful about the activities they partake with their dog, big or small. Too much strenuous activity is not good on growing bones, particularly in big dog breeds.

when are dogs full grown

The quick changes don’t slow down from there. In their second year, dogs continue to grow quickly, tacking on nine years of life in the space of one.

Now their bones and mental capacities are nearly set in stone, and at the end of their second year, they have just entered the prime of their life.

Dogs at two (age twenty-four in human years) are energetic and athletic, and it is during this time that most excel in their chosen activity, sport or otherwise. However, the differences in dog breeds become clearer in this stage.

Small dogs become full-grown within the first year of their life; most never get bigger than what they are then. Big dogs will continue to grow in size over the next year or sometimes even two.

This is why correct dog food and portion sizes are very important in a young dog’s life.

At three years of age, big dog breeds have fully developed their musculoskeletal systems, and the small dogs have settled into theirs a year ago. They are no longer growing and developing, but are finally adults.

The age to compare a three year old dog to is twenty-eight, full grown and grown up. After that, dogs age roughly around four years to every one of ours. So a six year old Chihuahua is the equivalent of a forty-year-old, and a ten year old Labrador is sixty-six.

Big or Small: Age is Finicky

The biggest debate between veterinarians and scientists is the age-old question about why small dogs live longer than their bigger counterparts.

In the rest of the animal world, smaller mammals cycle through life faster, turning old in the blink of an eye. But with man’s best friend, it’s the lumbering giants that have the shortest lifespan.

There’s no exact reason known for why a Pomeranian at sixteen can move around with the dexterity of an eight-year-old human, while a Great Dane at sixteen is inching along at the human equivalent of one-hundred-and-twenty.

when are dogs full grown

The biggest theory is that large dogs age at an accelerated pace. Every 4.4 pounds of body mass knocks a canine’s life expectancy down about a month.

Maybe large dogs’ fast growth pace lends them to a higher rate of abnormal cell growth and cancer. Or maybe the rapid growth rate of a large dog breed makes age-related diseases affect them sooner.

It’s unclear. Scientists plan to study it further, but for now, the theories range.

The Long and Short of It

What can be agreed on is that small dog breeds don’t suffer the same amount of growth-related health issues, like developmental disorders and gastrointestinal problems.

Breeding is thought to have a hand in it; heavy-handed genetic twisting by us humans to have dog breeds large and capable of working sooner might have created the unfortunate side-effect.

Not purposefully, but it seems that in creating large breeds, we may have picked faster aging genetic markers as well.

Whatever the case, large and small dogs age to fifteen in their first year, and add on a minimum four years to one afterwards.

Watching for signs of that accelerated age in large dog breeds might help dog owners enjoy their canine friends for a good eight to ten years, as well as careful consideration for a small dog’s comfort will allow fourteen to fifteen years of friendship.

Here’s a video showing a Rhodesian Ridgeback growing up!

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