Dog Tips

How Do Dog Years Work? 


Dog years are a cultural phenomenon. You may hear them referred to in many ways. Yet, what exactly is a dog year? You may have heard different explanations from different sources. 

It’s natural and even fun to wonder what ‘age’ our dogs are. Dog years also help us keep up with our dog’s health and ensure they are aging normally. However, there’s a lot of information out there, and you want to make sure you are using a reliable calculation method when computing dog years. Keep reading to understand more about how to calculate a dog’s age and when it is useful. 

Factors that Influence a Dog’s “Age” 

Just as with humans, some factors can make a dog age more quickly. Some of the factors to consider are: 

  • Size. In most mammals, larger size = shorter lifespan. This is true for dogs as well. Evidence shows small dogs with the same quality of life as large dogs will live, on average, five years longer than large dogs. 

  • Weight. As with humans, obese or overweight dogs will typically have a shorter lifespan and will be more susceptible to diseases like cancer or diabetes.  

  • Breeding standards. Studies have shown that purebred dogs live slightly shorter lifespans than mixed breed dogs, otherwise known as mutts. However, size trumps all, as purebred small dog breeds still live longer than mixed-breed large dogs.  

  • Lifestyle. Just as with humans, dogs who live healthy and active lifestyles can expect a longer lifespan. 

Calculating Dog Years  

Now that we have gone over some of the caveats about dog years, you might be wondering how to properly calculate a dog’s age. There are a few different methodologies that can be used to calculate dog years. We will learn a little more about how dog years work below! 

The “One-to-Seven Years” Conversion 

A popular method for calculating dog years is a simple conversion. This theory says that one year in human time is equal to seven years in dog time. This theory is based on information that makes sense: It takes 70 years as the average human lifespan and 10 years as the average dog lifespan, then calculates a dog’s age based on that assumption. 

However, this theory is not perfect. It does not account for your dog’s pre-existing conditions or overall health. There are many factors to dog aging, and these factors are not linear, so this theory should be looked at as a rough and likely inaccurate calculation. 

Looking at Genes 

There was a study done on molecular changes in dogs as compared to humans. This study aimed to figure out exactly how dogs age. The study had some interesting results. They found that a one-year-old dog is close to 30 years old in human years. (1) 

The study showed they grow steadily at this rate until seven years old when their aging starts to slow. From this study, a calculation was created that you can use. The calculation is Human Age = 6(Dog Age) + 31. 

This theory is also not perfect, however. The calculation can be complicated for the average person to understand. More importantly, the study it’s based on only studied Labrador retrievers. Labs are medium to large dogs, so this calculation may not accurately represent other breeds, especially small breeds that are known to have longer lifespans on average. 

American Veterinary Association Dog Year Calculation 

Where do the vets weigh in on the topic of dog years? 

The American Veterinary Association starts with the assumption that a one-year-old dog is 15 years old in human age. A two-year-old dog is nine years older in dog years, meaning a two-year-old dog is about 24 years old in human age. 

If you look at stages of development in dogs, this calculation makes sense. Although dogs typically lose all their baby teeth by six to seven months of age, human children don’t lose all their baby teeth until around seven or eight years of age.  

Dog reproductive ability starts at around eight to nine months. Human reproductive ability, usually marked by puberty, does not start until 1113 years of age. By this logic, it makes sense to assume a one-year-old dog is around 15 years of age in human years.  

This is the longest-standing theory, and it seems to be the most accurate overall. It’s also currently the only approved method of calculating dog years.  

Calculating Your Dog’s Age  

If you’d like to estimate your dog’s age in dog years, you can use this simple calculation to do so: 

  • A one-year-old dog = 15 years of human age  

  • A two-year-old dog = 24 years of human age  

  • After the first two years, add five years in human age for every one year in dog age. As an example, a three-year-old dog would be 29 in human years, and a five-year-old dog would be 39 years old in human years. 

This is just a rough estimate. To get more detailed, look at the size of your dog. Giant breeds (100 pounds or more) age less during the first two years of life. Giant breeds are 22 years old in human age at two years old. 

However, they age much more quickly. By age three, giant breeds are 31 years old in human age. This is calculated because small and medium breeds are fully grown by nine months old, while larger breeds continue to grow until 18 months old. 

Why Do Dogs Age So Fast?  

When looking at how dog years work, you might wonder why dogs age so fast in comparison to humans. There are a few reasons. Dogs have naturally shorter lifespans than humans, making them age faster compared to humans. Dogs also have a metabolism that is much faster than ours, which makes them age more quickly. Their hearts, bones, muscles, and joints also wear out much quicker than ours. 

Bottom Line 

We love our dogs, which naturally leads us to be curious about their health and wellness. Knowing your dog’s approximate age can help you better understand what stage of life they are in when comparing it to your own.  

Our dog’s age can also help us anticipate certain conditions and health issues that may come around. For example, diseases in dogs like osteoarthritis, arthrosis and elbow dysplasia are much more common the older a dog is. By knowing your dog’s age, you can begin to anticipate what they might be experiencing health-wise, which is invaluable.  

As you have seen in this article, dog years are a heavily debated subject. There are many ways of thinking when it comes to calculating a dog’s age. On top of that, dogs can age much differently based on current health, size, and exercise levels. Due to this, dog year calculations should only be used as a guide and not a definite fact. 

The best way to know your dog’s age is to have a vet check them for all signs and symptoms of aging. Veterinarians have seen lots of dogs through their lifetimes and can more accurately tell you where your dog falls.  

In the meantime, you can have a little fun trying to calculate your dog’s age. Maybe you can even celebrate your “30thbirthday together!  


Follow us on Instagram

Follow us everywhere else: