How to Tell How Old a Dog Is

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How Long is a Dog Year?

You have likely clicked on this article because you want to know how to tell how old a dog is. Well, you have come to the right place! Dogs age differently from humans, and it can be helpful to know how old your dog is and how old they are in human years. 

In this article, we will cover dog years to human years, how dog years work, and how to tell how old a dog is just by looking at them.

how old a dog is

What Are Dog Years to Human Years? (Ratio)

Dogs live for less time than us, meaning that relative to humans, one year is a larger percentage of their whole lives. This is what is meant when people talk about “dog years.” By knowing the ratio of human to dog years, you can better understand how old your dog is relative to a human. 

You may have heard the rule “1 human year equals 7 dog years”. It turns out that it isn’t that simple. Dogs reach maturity faster than us, so the first year is like 15 human years. 

The size of your dog will also play a role in how many dog years they are. Smaller breed pooches live longer than larger dogs on average. This means that one year for a large dog will be a larger percentage of its overall lifespan compared with a smaller dog; this is especially obvious during middle age.

Check out the dog age calculator below to find out more.

Dog Age Chart

Size of DogSmall 20 lbs. or less (<9 kg)Medium21-50 lbs. (9.5-22 kgs)LargeOver 50 lbs. (>22 kg)
Age of DogAge in Human Years
1 year in dog years151515
2 years in dog years242424
3 years in dog years282828
4 years in dog years323232
5 years in dog years363636
6 years in dog years404245
7 years in dog years444750
8 years in dog years485155
9 years in dog years525661
10 years in dog years566066
11 years in dog years606572
12 years in dog years646977
13 in dog years687482
14 years in dog years727888
15 years in dog years768393
16 years in dog years8087120

How to Tell How Old a Dog Is

The chart above can be a helpful tool to understand dog years, but what if you don’t know your dog’s age? What if you want to know how to tell if a dog is old or how to tell how old a stray dog is?

Some helpful tips can make aging a dog simpler, and these are shared below:


If you have adopted a puppy but don’t know much about their history, you may not know how old they are. 

Teeth can give you a clue as to what their age is. A puppy with no teeth or a few baby teeth will be less than 8 weeks old. Between 8 weeks and 7 months, puppies will have a complete set of baby teeth, which then fall out and are replaced by permanent teeth. A 7-month-old puppy will have a complete set of permanent teeth that are white and clean.

Corgi puppies sitting in a row

The eyes in very young puppies will be closed. At 10 to 14 days old, their eyes will open. The color of a puppy’s eyes will gradually change; the permanent color will remain after 14 to 16 weeks. 

Adult Dogs

Teeth can also be a useful indicator for adult dogs’ age. A dog that is 1-2 years old will have dull teeth and yellowing on its back teeth. By 3-5 years old, all teeth may be discolored and worn out. 

A dog that is 5-10 years old will have further wear and signs of dental disease. By 10-15 years old, the teeth are usually very worn out and have heavy tartar build-up. Some teeth may be missing.

dog tartar build up on teeth

Dental disease can be genetic and can also be affected by diet and husbandry. Smaller dogs are more prone to dental disease, so a younger, smaller dog may have teeth similar to an older big dog.

Body shape will change as a dog ages. A middle-aged dog will develop fat pads along its lower spine. By running your hands down their back, you may feel these. Muscle wastage along its back will make the spine more prominent and easier to palpate as a dog becomes senior. 

Muscle wastage will also be evident in a dog that has arthritis, a condition more common in older dogs. You may notice the muscle in their limbs is different if they have arthritis in one joint and not the others.

Cloudy eyes can be a sign that you have a senior dog. Nuclear sclerosis is a typical age-related change that occurs as dogs age. Another possibility is that your dog has cataracts; these can develop in dogs of any age and requires medical attention. If you notice your dog has cloudy eyes, get them checked over by a veterinarian.

Coat color will often fade, and areas of white will develop as a dog ages. You may notice white hair around eyes and muzzles but remember this isn’t always accurate as some dogs may be born with white fur, which is not an indicator of old age in these dogs.

Also, a dog’s hearing will often worsen as they age. If you notice your dog can’t hear the treat packet opening like it used to, this could signify that your dog is more mature. A veterinarian can examine your dog’s hearing to find out if they really can’t hear or if they are just ignoring you!

If you are still unsure, you can take your dog to your vet. Your vet will estimate your dog’s age based on a complete physical exam looking at the bones, joints, muscles, and internal organs. Lab tests can help assess the health and age of your dog.

Don’t forget; genetics, previous health issues, and lifestyle will affect how old a dog looks, and estimates may not always be inaccurate. A dog that has been a stray all its life will often look older than a pet dog.

If estimating your dog’s age is not accurate enough for you, there is a new genetic test available that can help identify your dog’s age more accurately. This test measures “genetic age”- which may not be the same as chronological age (i.e., their birthdate). The genetic age is a more accurate test for expected lifespan as it assesses your dog’s genes.

In Summary

As you may have realized from reading this article, it can be very difficult to accurately tell how old a dog is. There are some helpful hints, but adult dogs can be tough to age, and even veterinarians will struggle to give your pooch the exact age.

Physical changes, such as those to your dog’s teeth, eyes, and muscles (that you can examine at home or have your veterinarian check out), will provide clues about how old your dog is.

While you may not find out exactly when your dog’s birthday is, having an idea of age can be helpful to ensure the care you provide is appropriate for their life stage. Diet, exercise, and medical attention that is best for your pooch will change as your dog ages, and this can be personalized for your dog once you know their age. 

Working alongside your veterinarian, you can ensure your pup lives the most extended, healthiest life possible.

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Helen's journey in veterinary medicine is marked by her dedication to small animal practice and a thirst for diverse experiences. She graduated from Massey University in 2016, embarking on her career at a rural clinic in Canterbury, New Zealand, before venturing to the UK in search of new challenges. Helen's love for animals has always been at the core of her passion, and her dream of working with them has become a fulfilling reality.