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How Old is Your Dog?

Updated on: July 2, 2021
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For decades, dog owners have assumed that their pets aged about seven times as fast as their human counterparts. This made their one-year-old dog seven years old or their 10-year-old dog 70. A 100-year lifespan for a dog would be about 14 years old in human years. 

It turns out this common belief is a misconception. Dogs do age faster than humans, but the process is not as easy as equating one human year to seven dog years. 

According to a study published in the journal Cell Systems, the updated framework for assessing dog aging explains that the fastest period of aging in a dog’s life occurs within the first year. Each year after the aging process slows and the ratio of human-to-dog-years changes. In this new formula, the first eight weeks of a dog’s life equals about nine months of a human infant’s life. 

Researchers compared epigenetic changes and development milestones in human and dog lives. 

According to the information, the comparison of physiological milestones provides a better indication of a dog’s age. They also compared end-of-life situations and estimated the average lifespan of a Labrador retriever of 12 years to be equivalent to the average 70-year lifespan of a human.

Additionally, most researchers and dog owners acknowledge that not all breeds of dogs will age at the same rate and some have longer lifespans than others. For example, Labs tend to stay in their “puppy phase” for as long as two years. Smaller breeds tend to live on average three to five years longer than larger breeds. And of course, as is the case with humans, diet and lifestyle affect a dog’s aging process and how long he lives.

If you’re wondering how old your dog is and you aren’t sure how the new calculations work or if they apply to your dog due to its breed or a mix of breeds, read on to learn how to estimate your dog’s age.

How to Tell How Old a Dog Is 

There are several ways to assess your dog’s age. For instance:

Check Your Pet’s Teeth

Examining the condition of your dog’s teeth is a great way to get an idea of how old he is. According to the Humane Society of the United States, puppies develop teeth around four weeks of age. They still have their baby or milk teeth up to eight weeks old. These small, sharp teeth begin to fall out and be replaced by adult teeth around three to six months. 

How Old is Your Dog? 4

Dog’s teeth begin to show wear around age one or two. This includes light stains and plaque, especially on the back teeth. Around three years of age, your dog’s teeth will likely begin to yellow and have visible plaque. Five-year-old dogs tend to have a significant amount of tartar and their teeth might begin to wear down. This is usually around the time your vet will recommend professional dental cleaning.

It’s common for dogs 10 years of age and older to have missing, cracked, or loose teeth if you haven’t done multiple cleanings per week and professional cleanings. Keep in mind, the more you do to protect your dog’s teeth, the less wear and tear they’ll show, which makes it more difficult to use teeth as an age-determining factor.

Examine Your Pet’s Coat

Dog fur grays just like human hair as dogs grow older. Most dogs begin to develop gray hair around seven or eight years of age. Don’t worry, though, if your dog has gray hair younger than this. Again, like humans, some dogs go gray sooner than others. Stress and anxiety also exacerbate the appearance of gray hair.

How Old is Your Dog? 5

Gaze Into Your Dog’s Eyes

Older dogs tend to have cloudy eyes. Discharge is more frequent as they age, too. Waning vision health is a normal part of the aging process for dogs. Older dogs develop cataracts and can go blind. Most dogs begin to experience a decrease in visual acuity around six to eight years of age. This seems young, but don’t panic. It’s akin to needing reading glasses in middle age for humans.

How Old is Your Dog? 6

Check Your Dog’s Hearing

Have you noticed a decrease in your dog’s response time? If he’s growing older, it might be more about a hearing deficit than stubbornness. Younger dogs tend to have sharp hearing, but as they age, you’ll need to speak more loudly for your pet to hear you. Your veterinarian can check your dog’s hearing if you have any concerns.

Pay Attention to Your Dog’s Activity Level

Like humans, most dogs slow down as they age. The extra-exuberant puppy energy that gradually declined over the years is completely a thing of the past for a senior dog. But most older-dog owners will tell you, every once in a while they see signs of the puppy from years gone by. 

This is especially common when you introduce a new puppy into your home. Few things will energize an older dog like a new, younger friend.

The Ultimate Guide to Dog DNA Tests: What They Can Tell You.

Why Do Some Dog Breeds Live Longer than Others?

One of the primary differences between large breed and small breed dogs is how long the different sized breeds live. The lifespan of a large dog is usually about 10 to 12 years. Smaller dogs usually live at least 11 years, but some live up to 14 or 15 years. Giant breeds have the shortest lifespan of about 7 to 8 years. 

Researchers believe this is because large dogs use up their “growth energy” sooner than small breeds. This causes base damage to their cells because of oxidative stress. Smaller breeds have longer telomeres, which increases their lifespan.

Additionally, some research shows that breeds with long lifespans have a genetic resistance to potentially fatal diseases. Sometimes the length of your dog’s life will have nothing to do with his size. 

Breeds with a Shorter Lifespan

Giant breed dogs tend to have the shortest lifespans. There are no guarantees and your dog’s diet and lifestyle affects his lifespan, but in general, the breeds with the shortest lifespans (5 to 10 years) include:

  • Dogue de Bordeaux (5 to 7 years)
  • Great Dane (6 to 8  years)
  • Bernese Mountain Dog (6 to 8 years)
  • Irish Wolfhound (7 to 9 years)
  • Bullmastiff (7 to 10 years)

What to Do When Your Dog Gets Older

You can’t stop time, but you can slow your dog’s aging process and ensure that he feels his best for as long as possible. Many senior dogs live happy, healthy lives and remain active well into their teens.

What can you do to help your dog live his best life as a senior?

  • See your vet at least annually. Older dogs might need more frequent visits.
  • Ask your vet to perform a body condition assessment to determine if your dog is at his ideal weight
  • Feed your dog a healthy, age-suitable diet that limits “human” food (fruits and veggies are ok)
  • Make sure your dog gets daily exercise, even if he’s slow and tires quickly

How Can I Tell If My Dog is Aging Too Quickly? 

The goal is to slow the aging process as much as you can for your pet. This ensures he lives as healthy as he can for as long as he can. If you have concerns your dog is aging too quickly, consider the following:

  • Is my dog overweight? An overweight dog has a higher risk of certain diseases, especially as he gets older
  • Is your dog unenthusiastic? Your dog should be interested in his favorite activities, even as he gets older. If your dog has always loved going for car rides and suddenly he’s not interested, it could be due to a health problem.
  • Sleeping a lot. Most house pets sleep a great deal more than non-pet owners expect, but there is such a thing as too much sleep for dogs. If your dog has always been lazier as some breeds tend to be, it’s likely not a concern. But if you notice a gradual increase in sleep as your dog ages, it could be linked to arthritis or joint inflammation. Supplements can restore your dog’s energy and help him balance sleeping and waking time.
  • More bathroom breaks and/or bathroom accidents. If you notice your older dog is suddenly having indoor potty accidents, increase the number of bathroom breaks. Just like humans, aging dogs tend to need the bathroom more frequently and even throughout the night. Keep in mind, an older dog’s accident isn’t the same training issue as it is with a young pup. Have your vet evaluate your older dog if potty accidents are a problem.
  • Bad breath. Older dogs tend to have deteriorating dental health which affects the smell of their breath. Brushing your dog’s teeth daily or several times a week keeps tartar and plaque at bay and reduces the risk of many serious health problems.

 What Role Does Diet Play in a Dog’s Health and Aging Process?

In the same way, nutrition affects a human’s quality of life and the aging process, diet does the same for dogs. What you feed your dog has a dramatic effect on his aging process. And like humans, dietary changes are necessary as your dog ages. 

Adding supplements, limiting treats, and ensuring your dog is eating the proper amount of macronutrients is a great way to keep him healthy for as long as possible.

To ensure your dog’s diet is slowing and not speeding the aging process, make sure you know the following about your dog:

  • Daily caloric needs based on his age, breed, and activity level
  • Daily protein needs
  • Daily fiber intake and if it seems to be enough based on his potty habits
  • Mineral needs
  • How much water he’s drinking – older dogs are more prone to dehydration, especially if they have kidney health issues or are taking medications that are dehydrating

There’s no turning back time, but there are plenty of things you can do to help your dog age as slowly as possible. As your dog ages, make sure you understand how to help him feel his best and live as long as possible.

Check out our review of the Top 5 Best Dog DNA tests.



Coile, Caroline. “How to Feed the Senior Dog.” American Kennel Club, American Kennel Club, 28 Oct. 2016,

“NIH Researchers Reframe Dog-To-Human Aging Comparisons.” National Institutes of Health (NIH), 9 July 2020,

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