How Old Is My Dog? How To Calculate Dog Years

How old is my dog

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How old is my dog? Multiply your dog’s human age by 7 and there you have it, you get their age. Isn’t it that simple? Unfortunately, that’s not true. While we were accustomed to multiplying their age by 7 to get an idea of their actual age, recent studies show that there is more to it than multiplying their age by 7.

The 7:1 formula came in the 1950s and it seems to have stuck with pet parents because it is so easy to remember. Perhaps, veterinary doctors wanted to explain that while an average human lives for up 70 years of age, an average dog lives for 10 years. Thus came the formula.

Dr. William Fortney a veterinarian in Kansas State University, argues that the 7:1 formula was a marketing gimmick to encourage pet parents to take their dog to the vet at least once a year.

Background Study

Even before the exact formula was detected, scientists did realise that the 7:1 formula is very inaccurate. There are many things to consider when calculating a dog’s age. To start with, different breeds age differently. 

Smaller breeds reach sexual maturity much more quickly than bigger breeds and they live longer. Almost all dogs grow into their full size within their first two years which means that dogs grow faster during their initial years followed by a slow progression to old age.

So, a group of researchers estimated that for a medium-sized dog they turn 15 years on their first birthday. On their second birthday, they turn 15 + 9 = 24 years. From the next birthday onwards we add 5 years for every one year.

This is a very rough calculation and it doesn’t take giant and small breeds to consideration. However, the approximation set us on the right track and we started to realise that the 7:1 formula is not accurate.

By tracking the changes in our DNA, researchers are able to track our biological age. This process can be repeated for rats, chimpanzees, dogs and pretty much any other mammal.

So eventually, a group of researchers studied the DNA changes in Labradors and compared it with that of human DNA strands. They did find some similarities when they compared DNA strands from ageing dogs and human beings.

How Old Is My Dog

After conducting many studies, researchers concluded that the following as the new formula to calculate dog years:

16 x ln(dog’s age) + 31

They argue that dogs age rapidly during their initial years and as they grow older, their ageing becomes more and more gradual. You need a scientific calculator to calculate your dog’s age.

According to the above formula, a year-old dog is in fact 31, whereas a 5-year-old dog is 56. A ten-year-old dog is 67 and so on.


While this study is slowly gaining popularity and merit, it’s still in its early stages and therefore has scope for improvement.

The first criticism is that they only took Labradors in the study. So while the study can help us accurately prove the age of a Labrador it falls short in predicting respective ages of other breeds like Chihuahuas, Great Danes etc.

Different breeds age differently. So, while a Chihuahua can live up to 20 years a Great Dane lives only up to 8 years.

Why Do Small Breeds Live Longer Than Large Breeds?

This is a mystery even to scientists. Usually as the size of mammals increase, so does their lifespan. Elephants live for around 50 – 70 years whereas rats are lucky if they make it to their fourth year.

So, why then does a dog’s lifespan increase as they become smaller? Well, no one really knows why. Scientists predict that for every 1.9 kilos of a dog’s weight, their life expectancy reduces by a month. 

It is interesting especially because smaller dogs reach puberty much faster than larger dogs but they age slower once they reach adulthood. The chart below shows their approximate ageing based on their size. 

If you notice carefully, you will see that giant breeds are actually younger than small to medium dogs during their first two years. On their third year, they shoot up in the biological clock.

dog age chart; source:

Small, medium and large breeds age in a similar pattern until they reach their 6th year. That’s when smaller breeds start to age more gradually than the others. 

Can I Slow My Dog’s Ageing?

Of course, you can! Just by ensuring they have a healthy active lifestyle with a good diet, you automatically reduce their ageing.

As we said earlier, your dog’s lifespan reduces by a month for every 1.9 kilos they put on. Now, of course, this does not mean that you should keep your dog malnourished but keeping them on the lower side of their ideal weight range is a good way to keep them young and active.

keeping dogs young and active
The leaner they are, the easier it is for them to carry their weight. They put less pressure on their heart and invariably live longer.

The leaner they are, the easier it is for them to carry their weight. They put less pressure on their heart and invariably live longer.

Did you know that sedentary death syndrome affects both humans and pets? This means that if your dog has enough to eat, but not enough energy outlets, or in other words, if they live a sedentary lifestyle, they may become a victim to many chronic illnesses before their time.

So, if you want to increase their lifespan, you must ensure they have an active lifestyle. Take them to places where they can run and play. The more fun they have in their youth, the longer they will be around as they grow older.

At the end of the day, there’s no point living a long life if you aren’t having fun. So, stop counting their age and start making their life more interesting. As time passes by, you will forget the number of years you spent together and remember the fun trips you had together,

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About Dheepakh

About Dheepakh

Dheepakh is a dedicated pet parent. His love for his dogs turned him into a pet food enthusiast. He has dedicated all his life to understand pet food nutrition and is eager to learn everyday.

One Reply to “How Old Is My Dog? How To Calculate Dog Years”

  1. Info Hondenrassen

    Thank you so much for the valuable content of this blog. The age of the dog is important to know because everyone has the proper care.

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