How to calculate a dog’s age by comparing it to a human’s age

Let’s compare it with human age for a better understanding of your dog

Photo of author

By Kenny G

How to calculate a dog's age

How to calculate a dog’s age in human years: If you have a dog, you have probably wondered at least once how to calculate its age in relation to human years, “but I wonder how old Fido would be if he were a human?”

You may have been told that it’s easy, just multiply the dog’s age by seven… well, let’s say that this is a very rough approximation, and we can be more precise. Let’s better understand a more accurate formula for calculating your dog’s age compared to yours.

Early Development in Dogs: Why Multiplying by Seven is Incorrect

Let’s start with the established habit. The “seven dog years to one human year” rule has been widely spread, but it is not accurate.

Like most animals, dogs have a much faster development than humans in the early years of life, and in the theoretical equivalence between canine and human life, one year for them should “weigh” much more than one of ours.

We can consider a one-year-old dog not as a puppy anymore but almost like a teenager, while a seven-year-old child is still young.

We have already addressed the same issue for cats, and in that case, too, the rule of seven is incorrect. Here is our in-depth analysis: calculating equivalent ages for cats.

Now let’s go back to our canine friends: different breeds have different lifespans and rates of aging. For example, large breed dogs tend to age more quickly than small breed dogs.

Therefore, a “one-size-fits-all” approach to converting a dog’s age into human years is not accurate.

How to calculate a dog's age

How to Calculate a Dog’s Age: The Most Accurate Formula

There is a formula that many researchers converge on, which is based on how DNA changes with age. Its origin is complex, but we can summarize that it is based on how DNA changes with age.

The premise is that it is more accurate for dogs that are older than one year, as the growth and development of puppies are faster and more variable.

The formula is not very simple, and it might seem intimidating at first sight because it involves logarithms, a distant memory for many from their study days. But don’t worry, we will try to simplify it with many examples.

Equivalent age of a human = 16ln(dog’s age) + 31 years

Where “ln” is the natural logarithm, as I mentioned earlier.

I know that this might not make much sense to you, so let’s move on to some examples right away.

How old is a 5-year-old dog?

First example: a 5-year-old dog, and we want to calculate its age in human years.

The formula would be:

human age = 16ln(5) + 31 ≈ 57

You need an online calculator: you can find it here Natural Logarithm Calculator: just enter the current age of the dog in the X field, and it will automatically give you the logarithm.

Therefore, we can say that a 5-year-old dog is similar, in terms of aging, to a 57-year-old human. With the rule of seven, you would have said 32 years, and as you can see, the difference is considerable.

How old is a 7-year-old dog?

Let’s go higher.

human age = 16ln(7) + 31 ≈ 16*(1.9) + 31 = about 61 years

How old is a 10-year-old dog?

Let’s see this example as well.

The formula is simple: human age = 16ln(10) + 31 ≈ 68

Using the calculator I mentioned, it would be 16*(2.32) + 31 = 68 years, so a mature dog, ready for a well-deserved retirement. 😉

How old is a 15-year-old dog?

Now let’s exaggerate. It would be 16ln(15) + 31 ≈ 75 years, really old.

How old is a 20-year-old dog?

We’re almost at the top: 16ln(20) + 31 ≈ 81 years

Age of a dog at a glance

Here is  also a short table to help you:

Dog Age Human Age
5 57
7 61
10 68
15 75
20 81

But does the formula apply to all dog breeds?

It is, as expected, a good approximation. It should be noted that different breeds may have different rates of aging.

In general, the aging process is faster for “large” dogs compared to small ones. Therefore, a small dog, at the same age, may be “younger in human terms” than a large breed dog, and vice versa.

There are also other factors that can influence the accuracy of the value provided by the formula:

  • Diet, exercise, veterinary care, and the overall well-being of the dog can influence its rate of aging: proper nutrition, regular exercise, and good veterinary care tend to slow down the aging process.
  • Genetic predisposition is also important in longevity and the aging process. Some breeds may be more prone to certain age-related diseases, which can affect their life expectancy and therefore their relative age.

Our conclusions on how to calculate a dog’s age

Knowing your dog’s age in comparison to yours is not just a simple and enjoyable exercise.

It can help you better understand which life stage your pet is in and therefore adapt their needs to provide them with appropriate care. We hope that our guide has been helpful to you.

By the way, don’t miss out on all our other tips for your four-legged friends.

Everything about dogs and their care

Plenty of advice to keep them in the best shape possible, here is some other useful information about dogs:

Some dog breeds to discover

Discover some pet dog breeds you might like: