How To Tell How Old A Dog Is – The Most Accurate Way

A devoted pet parent, pet store manager and animal shelter volunteer. Read more about me here.

Today I'll teach you how to tell how old a dog is the most accurate way - backed up by science. 

This is a prominent question in the dog adoption circles and organizations, as the shelter dogs often don't come with history records. 

Still, if you're interested in learning how to determine a dog's age accurately, that means there's a quite big chance that you're adopting, and for that act alone, the whole community shares these words:

You're amazing! We wish there are more people like you. ❤️

Knowing the dog's age will help you develop a proper care routine for your new pet, including health checkups and proper practices for conditions such as vaccination. Furthermore, it will establish some ground rules in feeding, playtime, and get you closer to your new buddy.
Last Updated: October 4th 2023

Let's Talk About Dog Age
(& Calculations) In General

As we all know, dogs age way faster than us.

Their lifespan is shorter and their organ system is designed for up to 20-ish years maximum.

Since dog's life and development happens way quicker than human's, puppies will reach sexual maturity in a single year (I'm talking smaller breeds). 

On the other hand, after reaching maturity, the dog's life and development (again, it depends on the breed) continues in a steady pace, where it's way more difficult to pinpoint the exact age.

determining dog's age is way easier when he is a pup

When is my birthday, Mommy?

That's why it's way easier to guess the age of a puppy, and most people with some knowledge will do it right. 

Guessing an adult dog's age is quite trickier.

Every pet owner out there has heard some type of rule or way of determining a dog's age.

The most common one out there is the following:

Human Years x 7

Even though simple, this formula isn't the most accurate one. It was built on 1950's assumption that average human life expectancy is 77 years, and dog's life expectancy is 11 years.

Not quite the case now, right?

The truth is that it is a bit more complicated, and depends on several factors. I'll try to simplify it for you as much as possible;

You know the idea (and topic) of difference between chronological and biological age - where your overall condition & health status determines how old you actually are? 

The same logic applies on determining dog's age. Heck, it even favors the biological age more! 

Basically, that means how healthy your doggo is, the lower his/her's age will be. 

Speaking on this topic, some popular websites out there even offer dog age calculators to help you streamline the process.

Here's  WebMD's dog age chart that I'm positive you've probably seen already:

This chart is good, but overall, there's a way more accurate method & formula developed for it, and if you want to learn about it and use it, keep on reading! (Or if you're impatient, click here)

We can clearly see that smaller dogs live longer, and have significantly better chances to reach long age. 

But first, let's talk some general cues about dog age:

How To Tell How Old A Dog Is
- By Checking Teeth -

how to tell how old your dog is - teeth

Teeth can be one of the most tangible evidence for proving your dog’s age.

Puppy teeth can begin to drop out at approximately 18 weeks. After around six months, all these teeth will be replaced by adult teeth.

Therefore, you can check your dog’s age by seeing if there are any puppy teeth left. This can be done by looking at your pet chewing habit to relieve the itch and the pain as the adult teeth set and settle into the gums.

Another sign should be tartar build-up on teeth. From twenty to twenty-four months, tartar seems to form around the molars instead of the canines. By five years of age, this tartar will get clearer and begin to have an impact on the canines’ base.

One important thing, though - the genetics and dog's behavior play an important role. For example, smaller breeds are more prone to dental illnesses than ones. This affects the teeth structure and hardens the possibility to determine right age. 

Furthermore, if your dog was an aggressive chewer in young age, the teeth might have marks and distinct features that would make the guessing process quite more difficult. 

When your dog turns into the middle age, the incisors begin to wear down - this is one of the common features of the dog teeth, on which the guessing process is based.

Pro Tip: The food your pet consumes on a daily basis has an impact on aging. Kibble and meaty bones help with the tartar formation by postponing it significantly. Always keep in mind what you're feeding your dog - you can prolong its life! 

How To Tell How Old A Dog Is
- By Inspecting Hair, Skin, And Coat -

Like humans, dogs go gray in time - sometimes because of stress, not just by aging. Besides the genetics and breed type, dog's diet and stress determine its aging significantly. 

how to tell how old a dog is - by examining the coat and skin

Make a guess based on its grayness - how old is this doggo?

Here're some characteristics for dog hair and aging:

  • Middle to old age can be determined with greying around the muzzle and the top of the head or eyebrows. 
  • For reddish, yellow, and gold colored dogs, the top of their head and muzzle often turn white in the middle age.
  • For skin, elasticity can be a sign. You can notice your dog’s skin is losing elasticity, becoming dryer and losing muscle tone when it gets old. This is more evident when your dog does not exercise regularly, or the diet quality is poor. More on skin in the following chapters.

Generally, gray hairs first start showing up on dog’s muzzle and under its chin. Then the gray color spreads across the chest, ears, neck, and haunches. It usually starts between five and seven years old.

Gray hair can sometimes show up way earlier, either due to genetics or stress. In these cases, you still know that your dog is young, so don't worry.  

One more interesting fact about dog ageing and gray hair - if the dog experiences (or have experienced) some type of anxiety, is hyperactive or destructive when alone, it has a significantly larger chance to develop early muzzle grayness.

This conclusion came to be by a big, lenghty research and the result was published in Applied Animal Behaviour Science. 

Determining How Old A Dog Is
- By Examining Eyes - 

Look me in the eye and tell me the truth - where are the treats? 

Inspecting your pooch's eyes, you can determine its age. But just like with the coat and teeth, there are some caveats. 

Generally, dogs develop a bit of cloudiness in the reticle. It is somewhat bluish or grayish, depending on the breed and the age. But more importantly, the location of this discoloration is the main point to pay attention to. 

If the discoloration shows up in the center, that's a completely different situation - called lenticular (or nuclear) sclerosis. This is a common condition in dogs aged 6 to 8 years old, and it comes as a natural process of ageing. If your old pal's eyes have this discoloration outside of the reticles, that's a sign that it is not a lenticular sclerosis, and that you should take your doggo to the vet for further inspection. 

The most important thing is not to confuse lenticular sclerosis with cataracts, which can occur in any stage of a dog's life. The above mentioned features can point your attention and help you diagnose the problem, or realize it's time to visit the vet. 

Don't be afraid of the cataracts right from the start, though; some dog breeds like French Bulldogs and Staffordshire Bull Terriers are predisposed to cataract manifestation in young age, even in the age of two. 

Guessing How Old A Dog Is
- By Studying Its Behavior - 

How about some hugs, huh?

Every dog comes with his own personality and demeanor; some dogs are more energetic and playful while others aren't as lively and enthusiastic, regardless of the age. Depending on a dog's temperament & personality, you can definitely aim for age estimation without much error. 

How is this achieved?

Well, it's quite easy; with age, dogs deteriorate in energy levels and stop being cheerful to things that made them ecstatic before. They stop being active, start to sleep often and for prolonged periods, and have difficulties getting up or down, or climbing stairs. 

These changes are influenced by aging and age-related issues that come inevitably. Depending on how turbulent the life was for your beloved pet, the old age might bring conditions such as: 

  • Age-related osteoarthritis - due to the injuries that might have occured in the past 
  • Hypothyroidism - low hormone levels  
  • Dementia - will cause strange behavior, anxiety, disorientation
  • Cancer - unfortunately, many types of cancer happen in the old age
  • Gastrointestinal Issues and Incontinence - with age, dog's digestive system starts to wear down
  • Heart Problems - Different types of heart diseases 

Every condition that an aging dog faces will bring its energy and enthusiasm down, and with any symptom of irregularity you have to act fast and bring the best care possible to ensure your furry friend is not suffering.

Evaluating A Dog's Age
- By Following Its General Health & Condition -

Finally, your doggo's overall state of wellbeing is a general cue when it comes to age detection. Simply said, a younger dog will be leaner, more muscular, and full of energy and vigor. 

When a dog is not young, getting obese and lazy is a natural state of affairs. That means all those consumed calories often don't get burned, and if you don't care, you'll have a lazy, obese dog who's not happy to move at all. 

Furthermore, when we talk about physical appearance and fitness, the overall muscle mass gets lower with age, and it's often replaced with above mentioned fat storage. It all happens because of less moving and slower metabolism - both regular occurrences in older dogs. 

Some special cues of older dogs:

  • Dogs past their middle age and coming to the old age often have a bad odor that does not seem to fade away even with washing.
  • Deteriorated hearing in the later years can also be a sign even though your dog’s sense of smell seems not to change at all.

How To Tell How Old A Dog Is - The Scientifically Most Accurate Method

Ok, so we learned that the standard presumption of human years x 7 is not working. (Based on that calculation, some dogs who lived over 20 years would be 140 years old)

Generally, one's general assumption of age is how much time has passed since the birth. Commonly, this time is referred as chronological age

The advanced formula (From this extensive research) that I'm going to show you here calculates more advanced metrics into the equation, such as:

  • biomarkers of aging - the standard gene producing mechanisms, and various markers that help measure the age accurately
  • frailty index - body's overall status of health and disease handling based on age
  • methylation levels - scientists have found that different levels of changes in the body are directly connected with this carbon
The formula is: human equivalent age = 16 x ln(dog’s chronological age) + 31.

 The "ln" before the brackets represents the logarithm, and it's used there to explain the dog's quicker maturity and slower aging towards senior period of life, which is proven to be the most accurate one. This handy graph illustrates this the best way:

Small simplification: 

  • Green - The human age x 7 presumption
  • Blue - The ad-hoc rule impacted by logarithm (dogs mature faster, then aging slows down)
  • Black/Red - The exact formula of aging 

To simplify it the most, guys over at AjDesigner website have custom coded the most accurate dog & cat age calculator for all of us:

How to use this calculator:

  1. Select your dog breed
  2. Input the years (and months)
  3. That's it! The graph will show your dog's accurate years! 

You can also play with options tab, where you can set up human life expectancy (it's set on 70 by default) which affects the math as well. 

So, how old is your dog? Let me know in the comments section! 

Dog Aging - Things You Can Control

Since we know how to determine the dog's age most accurately, it's time to talk about the factors that could prolong your pooch's life. Those include:

  • Diet & Exercise - Be informed about the right amount of food & exercise for your dog in every stage of life.
  • Tick, Flea & Heartworm Control - Be prepared for these. Almost 90% of dogs experience some form of the above mentioned conditions. Prevention is the best cure!
  • Dental Health - Unfortunately, almost 90% of dogs under age of 3 experience tartar buildup. Regular brushes (change the brush just like you would change your own) and proper toothpaste will eliminate bacteria in your dog's mouth, which will affect the longevity. 
  • Regular Vet Checkups - Have a special bond with the vet and develop a trusty relationship. Having a regular checkup routine with a trained professional could help notice and prevent a lot of problems, which prolongs dog's life significantly! 

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If you have any comment or question, don't hesitate to ping me below!

About the Author

A devoted pet parent to two lovely creatures – Charlie the Cat and Jimmy the Dog – a full-time assistant pet store manager, and an animal shelter volunteer. I've gathered knowledge about pets for almost a decade, and it all started in a small store called Jack's Pets.

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