Dog Years Vs Human Years – The Age Gap Between Species

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By Allison Salonko.

Allison is a Veterinary Technician in the state of Indiana. She graduated from International Business College and Vet Tech Institute of Indianapolis with a degree in Animal Science and Technology in 2011.

Most folks are familiar with the idea of 1 human year equals 7 dog years.

Well, this rule is a little outdated, especially considering that it truly depends on the breed and size of the dog that dictates the speed with which they age. 

All mammals go through the same developmental timeline.

  • birth
  • infancy
  • youth
  • adolescence
  • adulthood
  • death

Researchers have had a hard time characterizing epigenetic features in aging animals, but our canine companions provide an opportunity for us to understand these challenges.

Dogs – Understanding The Age Markers 

Dogs share nearly all aspects of their lives and their environment with humans.

This includes factors that are associated closely with aging such as diet and chemical exposure, while also having similar observations of health and health care intervention.


Epigenetics is the process by which modification occurs in the genome.

This biological marker is then used to study and understand the aging process.

By comparing epigenetic changes in the developmental periods of the human and dog we are able to gain some insight into the canine aging process compared to humans.

Studies show that epigenetic changes are directly linked to specific aging stages that are shared among species.


Another important aspect of understanding the aging process between people and dogs is methylation.

Methylation is a part of epigenetics that researchers believe attaches to specific DNA sequences.

These methylation patterns change over time and have allowed for the development of mathematical models used to calculate aging processes called “epigenetic clocks.”

Dogs – The Chosen Species For Understanding Genetic Aging 

Dogs actually have the same or similar biological aging hallmarks as humans, just in a much more condensed time frame.

Usually, dogs will go through an entire lifetime within 10-15 years compared to a human’s 70 years. 

This is why canines have become the go-to species for comparing and understanding the genetics of aging with all mammals, including humans.

Comparing The Young To The Young And The Old To The Old 

There have been studies performed comparing dogs and humans at different age stages in life.

Researchers were able to identify similar age-related methylation patterns.

This data was seen specifically between young dogs and young humans or older dogs with older humans. Not with a mix of the two. 

There are also consistencies with stages of life and the behaviors and energy levels that are seen.

Such as, a 4 year old dog has the same activity level as a young human adult and a 10 year old dog walks with the same stiffness that a senior does. 

The same thing applies to emotional maturity.

A young human in their twenties may not reach their emotional maturity until their late thirties or forties like how a two year old dog is an adult but will continue to chew up things he’s not supposed to.

Most dogs will reach emotional maturity around 3 or 4.

The New Mathematical Equation 

As mentioned before the new mathematical equation is much different and more complicated than the old “multiply by 7” rule.

While a majority of the age studies were performed with Labrador Retrievers, this does mean that the data will be different for other dog breeds. 

The research performed shows that a 12 year old senior Lab is closely equivalent to a 70 year old human being.

Small Dogs – How Much Slower Do They Age Than Bigger Breeds? 

For the most part, a small or tiny dog will age in a similar mental and emotional capacity as a medium or large breed dog.

That is, until around the age of 6 years.

At that point, the medium and large breeds start aging at a slightly quicker pace.

Giant Breeds – The Heartbreakers 

Everyone that has had a giant breed like a Great Dane or a Mastiff will recognize the term “heartbreaker breed.”

This was coined because of the depressing nature of the lifespan.

Most of these gentle giants won’t live to see the age of 10. And that is actually really old for them. 

When calculating age, you can always assume a giant breed dog will cross the rainbow bridge much earlier than its smaller counterparts.

Breaking Down The Age Differences Between Dogs And Humans 

While the life span difference between a Labrador and a human is pretty significant, there have been minimal studies performed on all the breeds and comparing their aging to humans.

Because a small and toy breed dog ages much more slowly and can outlive larger breeds by several years, the results and data would be quite different. 

According to the research performed on Labrador Retrievers, they found that the methylation age markers show an 8 week old puppy would be close to a 9 month old human baby. 

The age in human years piles up quickly as a dog grows up.

By the time that a dog is 1 year old, they are closer to a 12-15 year old human’s age in maturity.

Puppies And Infants – Milestone Age Differences

Puppies age considerably faster than humans.

They will hit most of the major baby milestones within the first month of life.

Most of these age calculations are based on medium to large breed dogs such as Labradors. 


They are able to crawl between 15 – 21 days, as opposed to a human infant, which usually starts crawling around 6 – 9 months.


Typically by 28 days, a puppy is starting to walk with a wobbly gait and most infants won’t walk till closer to 11 – 14 months of age.


Puppies can be weaned from their mother’s milk by 5 to 7 weeks of age.

This usually depends on the mother and her tolerance for having puppies hanging off of her all day.

Human infants don’t stop breastfeeding until they are at least 1 year old and some mothers will continue until they are 2.

6 Months Vs 6 Years 

By the time that a puppy has reached 6 months, you could consider them to be the age of a 5 year old human.

This is the point in a young dog’s life where they learn the fastest and is an important time for training and socialization.

Similar to when a child starts going to school and is learning how to have manners and read and write.

1 Year Vs 15 Years 

As mentioned above, the research compares a 1 year old large breed dog to a 15 year old human.

You can usually see the similarities with their emotional immaturity and stubborn nature as they enjoy destruction, being hyper and showing attitude to their owners.

2 Years Old Going On 25 

There’s another large jump in age when a 2 year old dog is considered close to a 24 or 25 year old person. 

At this point, dogs still aren’t emotionally very mature, just like people.

They have a great metabolism and loads of energy still.

This should be a peak time of exercise, activity and emotional growth for both species.

Adulthood – Ages 3 – 8 Years 

For dogs, they are considered adults and no longer adolescents once they are around 3 years old.

This age is comparable to a human in their late 20’s, typically 28.

They continue to mature emotionally and will develop most of their personality by this point.

9 And Older – Senior Age 

The senior age for medium and large-breed dogs is around 8 years old.

They can still have plenty of energy and be active but may start showing some signs of their older age.

They may begin growing grey and white hair around the face and muzzle while being slower to get up off the floor in the morning. 

No longer being in their prime means that both dogs and humans need to be more careful about injury and illness.

12 And Up – Geriatric Age 

At the geriatric milestone, our canine companions will slow down considerably, maybe showing spurts of the young dog they once were.

Sleeping more and slower to get around are just some of the signs of our pups getting to the last stage in life.

Beating The Old Rule – Really Calculating The Age

Science has finally proven the old ‘multiply by 7’ as an outdated method.

According to the American Veterinary Medical Association (AVMA), the first year of life is about equal to a 15 year old human.

The second year of life is another 9 more years, so 24.

And after that, every human year is equal to about 4 or 5 more years old depending on the size. 

Getting The Most Out Of The Few Years We Have Them 

Our canine companions are unfortunately not with us as long as we wish they could be.

They leave a mark on our hearts for close to 15 years, making their loss a truly tragic one when that time comes. 

Not taking time for granted is important.

Be sure to spend plenty of hours playing, cuddling and enjoying the loyal and wonderful companions that are our four-legged friends.