How Old Is Your Dog? (Really...) | Highland Canine Training

We all grew up being told every year of a dog’s life was equal to seven human years.

So my Golden Retriever is four years old, and by those calculations, he is only 28, right?

It is actually much more complicated than multiplying 1 x 7. That idea came about sometime in the 1950s. It was a way to make determining a dog’s age simple. It was based on the calculation that, at the time, the average person lived to 70 and a dog’s average lifespan was 10. That’s how the one equals seven rule was born.

What does the science say?

Simplicity rules, but science tells us differently. A dog’s age actually depends on breed size, and the fact that a dog ages very rapidly in their first few years. For example, in terms of development, a one year old dog is almost equivalent to a human teenager; dogs from 1-99 lbs in their first year are equivalent to a human at 15 years old, while that large, 100lb+ dog is 12 years old in human years. Let’s jump to 10 years of age – a dog 20lbs or less would be around 55 years old in human years, whereas a dog 51-100 lbs is bout 66, and at over 100lbs they are almost 80 years old.

A dog’s breed and genetics play a huge role in the dog’s aging process. Also, factors like nutrition, lifestyle and the quality of vet care are huge factors in how a dog can age.

Research into how dogs age

Work continues to get the most accurate representation of how a dog ages.

In 2020, the University of California, San Diego School of Medicine used DNA methylation patterns to determine what a dog’s actual biological age might be. The formula is below:

Human age = 16 x (ln)dog age + 31 where ‘ln’ is the natural logarithm.

How to use the formula

Find the natural logarithm: Take the natural logarithm (ln) of your dog’s age in years. Most scientific calculators and phone calculators have a natural log function (ln).
Multiply by 16: Multiply the result from step 1 by 16.
Add 31: Add 31 to the result from step 2 to get the approximate human age.

This tells us that a five-year-old Labrador Retriever would be approximately 57 in human years. Biological age determines how time affects cells and tissues, while chronological age measures how many times we have circled the sun.

We have created the calculator below for you to use to discover how old your dog is, according to the formula.

Dog → Human Age Calculator

Uses the UC San Diego epigenetic formula: human = 16 × ln(dog years) + 31.

Dog age Units

Enter your dog's age and click Calculate.

Notes & assumptions

Formula is most accurate for Labrador Retrievers; other breeds may differ.
Works only for dogs older than ~1 month (ln requires a positive age).
Result is an approximation for educational use.

What to consider as your dog gets older

When it comes to a dog’s age, we want to be most concerned about when your dog begins to become a senior. Our responsibility shifts as we may need to make changes to their nutrition, activity, vet care and more.

Vets consider dogs to be a senior when they have reached 75% of their life expectancy. Small dogs (less than 20 lbs) are considered a senior at 9-11 years while a dog between 20 and 100 lbs, are considered a senior between the ages of 7-9 years.

As a dog gets older, there are several physical changes that come into play that we also need to be aware of. Grey hair starts to appear on their muzzle, their eyes start to become cloudy, and they can develop cataracts which can even lead to blindness.

Hearing can gradually diminish, and they tend to become less active. Also, as they age, they can lose muscle mass. Dental issues come into play with tartar buildup, losing teeth, and other dental issues. This is why, regardless of how we interpret how old a dog may be in relation to human years, we need to be in tune with changes as our dogs age to help them do it gracefully and keep their quality of life as high as possible.

In conclusion

So, when it comes to determining how old our dogs are in human years, we have come a long way since 1268, where an inscription at Westminster Abbey suggested the ratio was 9 to 1, Today, DNA methylation tells us a dog’s aging process is non-linear, they age faster in the early years, and that aging slows down significantly in the dog’s later years.

With this information, what have we learned? Enjoy your time with them; regardless of how they age, they aren’t here nearly long enough.