How to Calculate Dog Years: Knowing Your Dog’s Age More Accurately

Image showing a dog and her owner
Anna Smith
Written by Anna Smith

Another year is another milestone, so humans always keep track of their age carefully. On the other hand, dogs do not age the same way as humans so it can be quite difficult to find out how old they really are. Most of us have heard that seven months in human time is equivalent to 1 dog year, but as it turns out, our research and analysis proved that the 7:1 ratio is just a marketing plot hatched by dog food manufacturers. So in this article, we plan to provide the correct answer to the question “how to calculate dog years.”

There are different reasons why you should calculate your dog’s age accurately. Just like human beings, dogs have different nutritional and medical needs as they age. Senior dogs, for instance, need additional vitamins and minerals such as glucosamine for better joint health while puppies need calcium and iron for stronger bones and teeth.

cute dog on a table, avoid bad foods for dogs

Therefore, the goal of this article is to help you better care for your dogs by advising you on the topic of how are dog years calculated. We are going to explain more about the 7:1 ratio and why this method is not as accurate as some other methods such as the American Veterinary Medical Association method. By the end of this article, you’ll know exactly what kind of nutritional and medical care your dog needs so you’ll be able to fulfill them and make your dog live a longer, healthier life.

How to Calculate Your Dog’s Age

There are a great many different ways to calculate dog years. Before we get to the scientifically acknowledged methods, we will first elaborate on our previous statement saying that the 7:1 ratio is just a marketing plot hatched by dog food manufacturers. We will explain why we arrived at this conclusion.

The 7:1 Ratio

The 7:1 ratio has been around for a long time and is considered one of the easiest ways to convert dog years to human years. However, this formula is not very accurate. It is not a scientific way of knowing your dog’s age because we all know that small dogs generally live longer than larger dog breeds.

Golden retriever tempted by a piece of cake.

In other words, the 7:1 ratio may apply to some dog breeds, but not all. This method is too simple and does not take into account all the factors that may affect the calculation, such as access to health care and nutrition.

Lucky for us there are easier and more scientific ways on how to calculate dog years into human years. For example, according to the next method, you just have to check for physical signs so you can arrive at an educated approximation of their age.

Checking Physically

This method is intended to help those who haven’t the slightest idea how old their dog is because they don’t know his exact birth date. One good way of determining a dog’s age is by checking for some physical signs, such as:

Physical Signs #1: Teeth

Puppies usually have all their puppy teeth by the time they are eight weeks old. Their permanent teeth should be in when they reach 7-8 weeks old. Check the permanent canine teeth; these are the longest ones, which makes this the easiest way to determine their age up to 6 months old. If they have all of their permanent teeth and these are all clean and white, your dog’s age could be around 1 1/2 to 2 years or closer to 1 year old.


After two years, your dog’s teeth will start yellowing especially on their back teeth. Older dogs also have tartar build-up at this stage. At 3-5 years dogs will start showing wear and tear on their incisors. This will gradually increase as they get older. Significant tartar build-up and gum disease can be seen around five years old. Missing teeth is a sign that your dog has reached the “senior” years.

Physical Signs #2: Musculature

Muscle tone in young dogs is also more defined. This is because they are more energetic and like to play and frolic.

Image showing a woman running with her dog

Older dogs, on the other hand, are usually bonier or fatter due to inactivity. Stiffness is also a sign of aging among dogs.

Physical Signs #3: The Coat

Young dogs usually have soft fine coats while old dogs have thicker and coarser coats which are also sometimes oilier. Senior dogs could also have patches of white fur around the snout.

Physical Signs #4: Eyes

Lastly, check your dog’s eyes. Puppies and young dogs tend to have clear bright eyes without tearing or discharge. On the other hand, older dog eyes are usually cloudy or opaque.

Image showing Dog Lab Eyes

Now that you know your dog’s exact age, you might want to convert dog years into human years. The 7:1 ratio is one way to do that, but as we have established that it’s not all that accurate, let us introduce you to the methods that are accurate.

American Veterinary Medical Association Method

This method is the “general” way to calculate a dog’s age. To make calculation scientific and uniform, the American Veterinary Medical Association came up with this basic calculation:

  • Year 1 for a medium dog breed is 15 human years.
  • Year 2 for a medium dog breed is nine years for humans.
  • After this, each dog year equals to 5 years for humans.

For example, if your dog has been with you for three years this means that he or she is approximately 29 years old (15+9+5). You can just keep adding five years every year if you celebrate their birthday.

Image showing a dog running with something in his mouth

You can subtract this estimation by 2-3 years if your dog is a smaller breed since they tend to live longer or add to this by the same amount if your dog is of a larger breed.

Sexual Maturity

Just like humans, dogs reach an age when they can give birth to puppies. The time when puberty strikes differs from dog breed to dog breed, but one thing is clear: the most common indication that dogs have reached sexual maturity is their menstrual cycle.

Image showing two dogs playing in the park

Generally speaking, dogs reach this phase in their lives when they are around one year old. A modern school of thought suggests that the first two years of a dog’s life is the human equivalent of 0-25 years old. This method uses dog’s sexual maturity and life expectancy to approximate their age.

Breed Size

Another way to calculate dog age is by breed size. Breed size plays a role in their life expectancy and could be a good indicator of their age relative to humans. Small dog breeds usually live longer than bigger dogs. This is because big dogs age faster and show signs of aging sooner. Grey hair, lethargy, and joint pains usually manifest earlier in large breeds compared to small ones.

dog playing fetch with owner

For example, Great Danes have an average lifespan of 7 years while poodles can live for as long as 14 years. It is hard to say why big dog breeds age faster and have shorter lifespans compared to small dogs. Studies suggest it could be because large dogs have more of the growth hormone IGF-1 in their blood than small dog breeds.

If we follow the breed size method, all dogs regardless of size have the same age during the first five years in life. It starts to diverge when they reach six human years. Take a look at this table below:

Size Of DogSmall (20 lbs or less)Medium (21-50 lbs)Large (50+ lbs)
Age Of DogAge In Human Years

Making calculations based on breed size has become the “modern approach” to estimating a dog’s age in human years. Of course, there are exceptions to the rule. For example, a puppy from a small dog breed might mature quicker during the first few years of his life and a puppy from larger breeds more slowly at first. However, large dog breeds reach their “middle age” when they are five years old in human years while small dog breeds do not become “senior” dogs until they are 10.

Quick Calculation

Here is another formula to calculate your dog’s age in human years. This method only works if your dog is more than two years old.

  • Take your dog’s age and subtract by 2.
  • Multiply the answer by four then add 21.

Now you have your dog’s age in human years. For example, if your dog’s age is 10, then he is 53 years old in human years (10 – 2 x 4 + 21).

Image showing a medium size dog

However, this is just a rough estimate since this formula does not take your dog’s size into consideration. This formula is best used for small dog breeds. This method is still great if you don’t know your dog’s size and have to estimate in a hurry.

Dog Age Calculator

In the age of the internet, everything can be found online including dog age calculators. You can easily find them on the web by Googling it. However, before you select any calculator, you should know that not all of them are accurate.

Image showing two dogs sitting together

If you want to rely on an online dog calculator, find one that takes into consideration your dog’s weight and breed. This will give you a more accurate estimate compared to calculators that just ask you for your dog’s birthday.

How to Make Your Dog Live Longer

Generally speaking, dogs are already living longer compared to their ancestors hundreds of years ago. Medical and nutritional advances have allowed dogs to stay healthy. Dogs today also enjoy a better quality of life compared to their ancestors. But we understand that that might not be enough for you. All dog owners want to be with their dog for as long as possible. Therefore, now we are going to let you know how you can use the knowledge regarding your dog’s age to help them live longer.

Anticipate Health Problems

Regular check-ups with the vet is a great way to ensure that they remain healthy and comfortable their entire life. Large dog breeds are prone to joint problems once they reach a certain age so make sure you watch out for that.

Vet specialist examination sick dog,

You also want to be aware of the diseases that are prevalent towards a certain breed. For example, Great Danes are prone to thyroid problems and hip dysplasia while Chihuahuas are prone to tracheal collapse and luxating patella. Knowing about these potential problems beforehand can help you address them before they even happen to your dog. Just like humans, dogs can benefit a lot from preventive care, and this is made that much easier by knowing your dog’s age.

Monitor Their Weight

Another great way of ensuring their health is proper diet and exercise. Many dogs today are obese, but they can reduce their weight by keeping active. Daily walks around the neighborhood plus a healthy diet of vet-recommended dog food can help them stay at a healthy weight and avoid problems like obesity and blood pressure. The risk of such problems increase as the dog grows older, so you’ll want to be extra careful.

Pay Attention to Their Mental Health

Aside from physical health, a dog’s mental health is also important. Dogs love companionship so make sure that you find time to play with them or have them socialize with other dogs.

image showing a dog playing with her owner

Their personality might change a bit as they grow older. For example, they may not be as energetic anymore. In such cases, be sure to adjust the playtime and the game intensity accordingly.

Wrap Up

Dogs are man’s best friends so it is understandable that dog lovers like us want them to live for as long as they can. Proper care and diet can help extend their life expectancy. For example, Great Danes live for an average of 7 years, but there are those that lived to celebrate their 11th year.

Remember that aging in dogs depends on breed, size, and diet, and there’s a lot we can do as dog owners when it comes to the last. As dog owners, it is our responsibility to know their age so that we can plan their nutritional needs and medical requirements early on.

Image showing a dog laying down on the sand

Have you tried calculating your dog’s age using any of the methods above? Which one of them do you think is the most accurate way of determining a dog’s age? Do you know of any other methods that you think deserve to be in this article? Tell us by leaving your comments below.

About the author
Anna Smith
Anna Smith

Anna Smith resides in beautiful Santa Monica, CA, where she works as a Pet Nutrition Expert in a leading retail pet store. She is responsible for nutritional strategies for different breeds and development of new products on the market in compliance with Association of American Feed Control Officials. Anna's passions are education about proven methods and best practices in the industry and her dog Max, who is always well-fed.