Dog Age Chart: Discover Age in Human Years by Size

Written by Amber LaRock
Updated: July 21, 2023
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Many of us have been told that one dog year is equal to seven human years. Though we’ve used this formula for years, studies now show that this comparison is not accurate.

Today, we break down recent studies on the canine aging process, and help you better determine just how old your pup is in human years!

Let’s get started.

How Quickly Do Dogs Age? Here’s What Science Says!

Senior Golden Retriever resting on a dog bed

The seven-year age rule in dogs is not as accurate as we’ve been led to believe!


We have been told for many years that dogs age at a rate of seven years for every human year. While we know that dogs age much faster than you and I, this seven-year rule is not quite accurate.

Experts now believe the ‘7-year rule’ may have been created in an effort to stress the importance of regular health checks due to how quickly our canines age. Thankfully, researchers have found a more accurate way to determine a dog’s age in human years.

Researchers examined the aging process in both humans and dogs by comparing their DNA. They looked for patterns in each of their DNA and examined how these patterns changed over time. By doing this, they came up with an accurate formula to determine a dog’s age in human years.

(human_age = 16ln(dog_age) + 31)

Let’s Make That Easier!

This formula is pretty complex, so let’s break it down! According to the American Veterinary Medical Association (AVMA), this is how you can best determine your dog’s age in human years:

  • The first year of a dog’s life is equal to 15 human years
  • The second year of a dog’s life is equal to about nine more human years
  • Once they reach three years of age, each additional year is equal to five human years

Keep in mind that the above rule roughly applies to small and medium sized dogs, so larger canine friends will age at a faster rate once they reach six years of age.

Dog Age Chart – Age in Human Years by Size

girl 9 years old with long hair model with a pet dog Maltese schoolgirl at home lifestyle on a beige background allergy veterinarian

Large dogs age at a faster rate than small dogs.


We’ve created an easy-to-follow chart to help you determine your dog’s age:

Age of the DogUp to 20 pounds
(human years below)
21 – 50 pounds
(human years below)
50 pounds and more
(human years below)
1 year of age151515
2 years of age242424
3 years of age282828
4 years of age323232
5 years of age363636
6 years of age404245
7 years of age444750
8 years of age485155
9 years of age525661
10 years of age566066
11 years of age606572
12 years of age646977
13 years of age687482
14 years of age727888
15 years of age768393
16 years of age8087120

Why Do Large Dogs Age Faster Than Small Dogs?

Research is still ongoing as to why small dogs seem to live longer than large dogs. Some scientists believe that since large dogs experience accelerated growth at the beginning of their life, they may be at risk of abnormal cell changes in their senior years. However, this theory is not yet proven.

Maybe one day we will have the answer!

Things To Keep in Mind as Your Dog Ages

Since our canine friends age at a much faster rate than you and I, it’s important to have your dog assessed by a vet regularly. We suggest scheduling a wellness exam with your vet once a year until the age of seven, and twice a year from eight years of age and on.

Yearly wellness exams can help your vet detect any changes in health, as many health complications are challenging for pet owners to detect on their own. Your vet will also recommend annual senior blood testing once your dog is eight years old, as dogs have an increased risk of health decline once they enter their senior years.

Final Thoughts

As we discussed above, a dog’s first year of life is equal to 15 human years. Their second year is equal to about nine more years, and each additional year after that is equal to five human years.

Be sure to check out the chart above to figure out just how old your pup is in human years!

The photo featured at the top of this post is © Hana Hanigerova/

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About the Author

Amber LaRock is a writer at A-Z Animals primarily covering topics surrounding pet health and behavior. Amber is a Licensed Veterinary Technician with 12 years of experience in the field, and she holds a degree in veterinary technology that she earned in 2015. A resident of Chiang Mai, Thailand, Amber enjoys volunteering with animal rescues, reading, and taking care of her two cats.

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