Published: February 9, 2018  

Last updated: March 2, 2025  

Author: Debi McKee

The first question most people ask about your dog is what breed he is. The second question is, how old is he? But when adopting a dog, we don’t always know the dog’s history.

Dog rescues and humane societies usually take a guess based on certain physical appearances. It can be difficult to know how to tell how old a stray dog is.

While you may never know your dog’s exact birth date, there are several physical attributes to look for that can give you a good estimate of how old your dog really is.

All of these vary based on your dog’s breed, nutrition, and medical history.

Our first foster dog, Silla, was an owner surrender, so we did know her age… she was 10 years old. The vet was actually shocked to learn how old Silla was because her teeth were still pearly white, which is very rare for a dog her age.

So how can we tell the age of an adopted dog? Here are three big clues to help you guess as close as possible:

1. Teeth: The Most Reliable Indicator

A dog’s teeth change significantly as they age, making them one of the best ways to estimate their age. See the chart below:

Checking Your Dog's Age By His Teeth, dog with mouth wide open showing teeth. Describing each level of tartar buildup to the age of the dog.


By the time your dog is about 4 months old, his adult incisors, canines, and premolars should be coming in. When your dog is about 6 months old, all of his baby teeth should be gone.

If your puppy has any baby teeth left, he is most likely younger than 6 months old.

Teeth of a 3 year old dog

If you have adopted an adult dog, it is going to be more difficult to determine age by his teeth. But you can guess that the more tartar builds up, the older the dog is. If his teeth are pretty clean, my guess would be he is younger than 3 years old. The above photo is of our 3-year-old yellow lab.

2. Is your dog turning grey?

This one is pretty simple; just like humans, dogs can turn white or grey as they age. Usually, around 5 years old, you will notice some graying around your dog’s face and muzzle. But greying is not always an accurate sign, as some dogs have been known to start graying as young as 2 years old.

Senior dog showing signs of grey and aging eyes

3. Observe your dog’s eyes.

Gaze into those beautiful puppy eyes. This is something I never knew before, but as your dog ages, his eyes develop lenticular or nuclear sclerosis. It looks like a haze or grey film over the eye.

And as your dog gets older, the gel inside the lens becomes thicker, hardens, and changes color. This graying in their eyes usually starts around 5 years old and becomes more prominent as the years pass. There is a great article on PetMD, Is it a Cataract or Lenticular Sclerosis?

If you are concerned at all about your dog’s eyes, I recommend taking him to the vet to have it checked out.

With these three clues – teeth, coat, and eyes – you can get a good estimate of how old your dog really is. But you also need to consider the breed of your dog. Larger dogs age more quickly than small dogs.

Dog Years Versus Human Years

So now that you have an idea how old your dog is in dog years, you may be wondering how old is my dog in human years?

How long is a dog year anyway?

I found it interesting that the common theory that one human year equals seven dog years is not true! I believed this my entire life until recently!

It turns out that a one-year-old dog is one in dog years but 15 in human years. Wow, that’s some quick maturing. This goes for all sizes of dogs.

But after about 5 years old, the conversion changes based on the size of your dog. Below is a great dog years converter chart to show how old your dog is in human years:

Dog Years Converter Chart

Chart showing the age of dog in human years by size of the dog.

Now that we have dog years explained clearly, enjoy every day, every month, and every year you have with your dog. Time passes so quickly!

Keeping your dog happy and healthy is the most important part of your life together. Feed them high-quality food, bring them to the vet for yearly checkups, and give them plenty of exercise and love.

About the Author

Debi McKee

Debi McKee is the expert behind Rescue Dogs 101 where she guides you in your journey of adopting and raising a rescue dog every step of the way. She is a mom of 3 human kids and 4 dogs and volunteers for a local dog rescue and Humane Society. Click here for more about Debi and her passion for helping you and your dog.

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  1. I adopted my dog from a rescue 1 month ago. Today she got spayed and had dental work done and my vet says she's more than 5 years old. He had to extract 10 teeth! He also noticed an internal incision just below where he made his incision for her spaying, but did not see an external incision. Any suggestions? My Vet has no idea why there would be an internal incision. Thank you! I can't see any greying of her hair because her hair is white (She's a Bichon Frise)

  2. I havea rottweiler german shepherd mix puppy shes about 16weeks. When she starts nipping i take my thumb and place it just a little behind her nose and my middle and pointer fingers under her lower jaw and put a little pressure and tell her no sternly.. it dont hurt her. But SHE STOPS.. the issue im having is she will go to the bathroom when i take her outside but not even five mins after i take her back in the house she goes again on the floor. No matter how long i stay outside with her. Help.. lol

  3. I was given a rescue Border collie dog in a pitiful state, and supposedly 8 years old. But I am sure she’s a lot younger: no grey round her muzzle, beautiful clear eyes and virtually no plaque on her teeth. She is high-energy, and very much appears to be only a year or so old, reminiscent of my previous lovely lass we acquired at five months. She has a lovely temperament learns very quickly, and has a sweet face. As I am disabled, I would like to train her to become an assistance dog, but am not sure if I can do it or need professional help with her.
    Any ideas most welcome!
    Hannah and Hollie the collie – woof!

  4. Okay so what about the dogs that have been very well took care of and given treats food and all needed to prevent the build up om the teeth is it possible that they are mistaken a 1-2 year old dog with a 3-4 ????? I just dont understand how a shelter can say oh this dog is 1 or 5 or whatever when there’s no absolute way to tell

    1. You are right, there is no absolute certainly unless you know the original owner of the dog. We had a 10 year old foster dog that the vet was shocked that she was that old because her teeth were perfect. So yes, it’s an estimate.

  5. I have resued many dogs and cats in my 77 years. I have found they make great pets. I have only had 1 dog I bought from a breeder. A mini grayhound. I had him from 5 weeks old to 23 years. He was my fur baby for sure. He was born with only 3 feet. He also had secures, but I did not care. I treated and loved him like my real baby. We were never apart except when I had my heart attack and then only 3 days. I could not stay away from him. We were inseparable. He has been gone 2 years now and I still cry and miss him. I dohave another rescue and he is great, but not my Itabit.. ( that was his name)

  6. Most of the observations are valid, but I disagree with the White/gray hairs around dog’s face and muzzle. B’cuz Black Labs who have been under a bit of stress can acquire early gray hairs.

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