Dog years human years

Dog Years to Human Years: What You Should Know

dog to human years

Even before the establishment of a general rule for the calculation of dog years to human years, the common notion has been that years of one dog year equals 7 human years.

In an attempt to explain how the 7:1 ratio formula came to be, it is said to be based on the statistics that humans live an average of 70 years while dogs live an average of about 10 years. 

Well, this belief has been in use for so long a time, but the truth about it isn’t so cut-and-dried. However, the use of this formula or method of estimating dog years to human years hasn’t stopped a lot of people from seeing this calculation as default and somewhat a general way of calculating dog to human years.

According to Kelly M. Cassidy, a researcher on the longevity of dogs and also the overseer of the Charles R. Conner Musem 1Charles R. Connor Museum at Washington State University erasing the seven-year rule in dog years is something that you can’t kill.

Similarly, according to William Fortney, who is a veterinarian at Kansas State University,2Kansas State University “I suggest that the 7:1 ratio of dog years to human years is simply a marketing strategy as well as a way to enlighten the public that dogs ages faster than humans, especially when viewed in terms of health.” More so, he added that it is also a way of encouraging pet owners to bring their pets for a check-up at least once every year.

How to Calculate Dog Years to Human Years?

According to the American Veterinary Medical Association, American Veterinary Medical Association calculating dog years in human years has been broken down as seen below as a general guideline.

> The 1st year of a medium-sized dog’s is equivalent to 15 human years
> The second year of a dog is equivalent to about nine of human years
> Three years and above for a dog year is equivalent to about five human years.

Why Smaller Dogs Live Longer than Larger Dogs?

The answer to this question is what scientists are still yet to find a convincing answer since they are still in awe of this phenomenon in dogs. Similarly, scientific research is yet to give a concrete explanation to the relationship that exists between a dog’s life span and its body mass.

When looking at other groups of larger animals such as whales and elephants, they live longer than smaller animals like rats, and this usually stirs the question of why smaller dogs live longer compared to the larger breeds.

In an attempt to give an answer to this question, it is believed that the reason why larger dog breeds have an accelerated life span is due to an increase in body mass.

According to findings report to Inside Science from a Cornelia Kraus who is an evolutionary biologist at the University of Göttingen in Germany, it was concluded that for every 4.4 pounds of body mass in dogs, there is a synonymous reduction in her life’s expectancy with about a month.

Although a concrete reason for this fact still remains unknown, Kraus was able to give some possibilities, which include the fact that larger dog breeds are quick or easily susceptible to age-related health challenges. Similarly, it was added that the fast pace of growth among larger dog breeds is also a reason for their higher chances of abnormal cell growth and death, which may arise from cancer.

In an attempt to further explain in detail, the link between growth and mortality, scientists are making future plans to carry out in-depth research on this.

dog years in human years

How Researchers Decided How Dog Years to Human Years are Calculated?

Although there are a lot of factors that need to be considered when considering the dog years in human years, reports from the AVMA has it that small dogs and cars are usually seen to be ‘senior’ once they are up to about seven years old – yes, you may cut in that at age seven, there is still lots of life in cats and small dogs at that age.

On the other hand, larger dog breeds seem to have a shorter lifespan when compared to small dogs. The larger dog breeds are usually considered to be ‘senior’ when they have attained at least the ages of 5-6 years.

The basis for this ‘senior’ classification in dogs is based on the fact that pets usually age at a faster pace when compared to a human, and this usually helps veterinarians to start noticing a lot of age-related challenges among pets once they have attained this age range. And in an attempt to oppose the common belief, dogs don’t age at the ratio of 7 human years for one dog years.

A typical illustration of this is in the Great Dane3Great Dane with an average life expectancy according to the Great Dane Club of America to be 7-10 years. What this means is that a Great Dane that is about 4-years old would have already been about 35 years of age when comparing this type of dog to human years. However, you shouldn’t forget that these numbers and statistics are only but a rough estimate of the true figures.

Similarly, the National Center for Health Statistics isn’t saddled with the responsibility of keeping dogs. Instead. What they do is collect data on dogs’ longevity from three main sources thus; veterinary hospitals, breed-club surveys, and pet insurance companies.

Epigenetic Clock Study on How Dog Years are Calculated

In a 2019 research42019 research carried out by the University of California San Diego, it was reported that a new method for the calculation of dog years was based on some changes that occurred in the DNA of both dogs and humans over a long period of time.

Among dogs and humans, it was reported that methyl groups are the recent addition to the DNA molecule over time, and this, in turn, alters the activity of the DNA without causing any visible change on the DNA itself.

As a result of this, DNA methylation has been a tool used by scientists to study the process of aging in humans in a process referred to as “the epigenetic clock.” 

In order to come up with the ratio for dog years in human years, scientists carry out a target DNA sequencing in about 104 Labrador Retrievers with an average age range of 16 years. This was in an attempt to compare the epigenetic clock in dogs to that in humans.

Results obtained from the research was used to establish the formula which is used for dog years calculation by comparing dog years to human years, and this was done by multiplying the natural logarithm of the dog’s years by 16 and then adding 31, and thig gives the human age

Mathematically, 16ln(dog age) + 31 = Human age

However, it should be noted here that the study was carried out using a single dog breed. So, what this means is that your dog’s breed (different from what was used in the research) years to human years using this formula may not give you the true value but only an estimated value.

More so, it is an established fact that different dog breeds age differently, and so the USCD formula may be lacking in giving you a definite result on how many dog years to human years


Dog years vs human years seems to be a controversial estimate for a long time.

In an attempt to estimate how many dog years to human years, the breed and size of a dog has to be considered in order to give a definite comparative value for both.

Mathematically, what is dog years to human years can be calculated using the formula

16ln(dog age) + 31 = Human age.