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The Truth About Dog to Human Age Conversion

Learn how to convert your dog’s age to a human age.

You might have heard the common saying that a dog ages 7 human years for every calendar year they live. That's not exactly right, though. It's quite a bit more complicated. Here's the real scoop.

Dogs Hit Puberty Early

As you know if you've ever raised a puppy, the first year brings a tremendous amount of growth and change. In fact, by the end of their first year, a dog is equivalent physically to about a 15-year-old person. Dogs go through their version of puberty around 6 to 8 months of age. Female dogs have their first heat then and are able to breed. By around 7 months of age, all of a dog's adult teeth are in.

The First 5 Years of a Dog's Life

After the first year, aging slows down a little, and by 5 years of age, dogs are the equivalent of around 36 human years old. That's still pretty close to the old adage that 1 year equals 7 human years for a dog. But after 5 years, canine aging differs depending on whether you are talking about a small, medium, or large breed dog.

The Difference in Aging for Small, Medium, and Large Dogs

Small dogs live longer than large or giant ones, and that translates to slower aging relative to human years once the first 5 calendar years are over. Small dogs age the equivalence of around 4 years per year, medium dogs range from 5-7 per year, and large dogs age from between 5 and 9 human years per one calendar year.

What this all means is that if a dog lives to be 15 years old, his human age equivalence is:

  • 76 years old for a small dog
  • 83 years old for a medium dog
  • 93 years old for a large dog

This can all be slightly confusing, and of course, there is some variation among breeds within the general size ranges. Giant breed dogs, for instance, have an average lifespan of 7-10 calendar years.

Here's a basic chart to give you an idea of the human age equivalent for a dog in the three main size ranges of small, medium, and large.

(Mansourian, 2015)
Size of Dog Small Medium Large
Age in Years Human Age Equivalent Human Age Equivalent Human Age Equivalent
1 Year 15 15 15
2 Years 24 24 24
3 Years 28 28 28
4 Years 32 32 32
5 Years 36 36 36
6 Years 40 42 45
7 Years 44 47 50
8 Years 48 51 55
9 Years 52 56 61
10 Years 56 60 66
11 Years 60 65 72
12 Years 64 69 77
13 Years 68 74 82
14 Years 72 78 88
15 Years 76 83 93
16 Years 80 87 120

How to Help Your Dog Live a Longer and Healthier Life

Now that you know about what human age your dog is equivalent to, you might be wondering how you can help your dog live longer and stay healthier. Here are some general tips and links to articles with more information:

  • Keep your dog at a healthy weight. An overweight dog is at much higher risk of developing painful arthritis, deadly diabetes, and life-threatening heart disease, all of which can shorten her life and add pain and suffering.
  • Visit your veterinarian often. Routine exams, preventative medications and vaccinations, and regular lab work can all help your dog stay healthy longer. As your dog ages, your visits to the doctor should become more frequent, so the doctor can catch and begin to treat problems as early as possible.
  • Monitor your dog's health and behavior closely at home. You are your dog's first line of defense against health conditions. As the person who is with your dog the most, you know what's normal for him. If you see anything out of the ordinary, get your dog to the vet and report it right away. For instance, an increase in water consumption, decrease in energy, change in appetite, or limp could all indicate a problem that should be addressed as soon as possible.
  • Keep your dog mentally stimulated. It's common for people to walk and play with their dog less as he gets older. Be sure to avoid doing that. Your dog can live a full, enriched life well into his senior years, but you'll need to maintain interaction, activity, and novelty in his play environment.

Works Cited

  1. Mansourian, E. (2015, Nov. 17). How to Calculate Dog Years to Human Years. Retrieved from

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