Human Years vs. Dog Years - Calculate your pet's age today!

The “one dog year equals seven human years” method has been around for a while, it’s not as accurate as we’d like. Calculate your dog's age using the age chart within this blog.

Human vs. Dog Years

Most people use the equation: one year of a dog’s life is equal to seven human years…we are here to debunk this myth. The truth is that this method isn’t entirely accurate. 

Historically, the “one dog year equals seven human years” method was created to simply show that dogs age much faster than their humans. Today, scientists and researchers have developed a more precise method of calculating a dog’s age to human years.

Let’s dig right in…

How do I calculate my dog’s age in human years?

If you’re looking to calculate your dog’s age in human years more accurately, you can now use this new formula created by researchers at the University of California San Diego School of Medicine. 

These researchers studied the way human and dog DNA changes over time specifically looking at patterns called methyl groups in humans and Labrador Retrievers. From this research, they concluded that you can calculate a dog’s age to human years by multiplying the natural logarithm of the dog’s age by 16 and adding 31. Their formula looks like this: (human_age = 16ln(dog_age) + 31). As you can see, this formula is pretty complex.

For an easier (and also seemingly accurate) way to estimate your dog’s age, you can follow this chart  for small, medium, and large dogs under 100 lbs.

  • The first year of a dog’s life is equal to 15 human years. 
  • The second year of a dog’s life is equal to about nine human years.
  • Each additional year is equal to about four or five human years.

So, you’re probably wondering why this is more accurate than the “one dog year equals seven human years” method.

Best way to explain this is that it takes into account that not all dog breeds age in the same ways. In general, we do know that smaller breeds tend to live longer than larger breeds.  Therefore, it’s helpful to break down a dog age chart in terms of size, as you’ll see below. 


Generally, you can group dogs into four different categories: small dogs (under 20 lbs), medium dogs (20 to 50 lbs), large dogs (50-100 lbs), and giant dogs (100+ lbs).

Use this chart to calculate your pet’s age in human years!

What are common signs of aging in dogs?

Physical and behavioral clues can be looked at to also help determine your pet’s age.  For example, teeth can be a particularly good indicator of your dog’s age. As PetMD explains, by seven months old, all of your pups permanent teeth are grown in; by 1-2 years, they’ll be duller and might have some slight yellowing; and by 5-10 years, they’ll show wear and possibly signs of dental disease.

Other indicators of your dog’s age, especially as they reach their senior years may include:

  • Graying hair
  • Poor eyesight, cloudy eyes
  • Trouble hearing
  • Stiff muscles and joints, arthritis
  • Lower activity level
  • Behavioral changes such as increased anxiety,
    confusion, accidents in the house, irritability, etc.

Of course, if you’re having trouble calculating it yourself you can always turn to our veterinarians for an accurate estimate of your dog’s age!  Your veterinarian will consider factors, including your pet’s teeth, body shape, hair or fur, and eyes, etc. to give the best estimate of their age.

Why is understanding my dog’s age important?

Main reason you should want to know your pet’s true age is to better understand how old they are and how they are aging.  This will allow you to understand how to properly care for them and give them the best life possible. 

Keep in mind, if you have a larger dog, you’ll want to start looking for signs of aging around five or six, whereas smaller dog owners might not see any real signs of aging until their dog is about seven or eight. Once your dog reaches their senior years, you’ll want to keep an extra close eye on their behavior, activity level, and eating habits. In general, a healthy diet and weight, consistent mental stimulation and physical activity, and regular check-ups at Brook Farm Veterinary Center will all help prolong your dog’s life expectancy. Additionally, you may want to consider investing in pet health insurance to cover unexpected accidents and illnesses. After all, your dog deserves the best care possible no matter how old they are.

At the end of the day…

Even though the “one dog year equals seven human years” method has been around for a while, it’s not as accurate as we’d like.  We encourage you to use the chart above for a more accurate estimate of your pet’s age based on the size of their breed. 


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