The Correct Way to Calculate Dog Years

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The old saying goes even a broken clock is right twice a day. If you're going by the premise that one dog year equals seven human years, the broken clock is right more than you are. Once in your pup's life that equation might be right, but exactly when depends on his size and breed.


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Canine Aging

Dogs age at a faster rate than their human friends. Think about your dog during his puppy months: He packed a load of growing in during that formative first year. On the average, a dog will age to the level of a 15-year-old human during his first year.


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By a year old, you might have been standing and taking your first tentative steps. By your dog's first birthday, he should have an understanding of basic commands, is sexually mature, and may be transitioning from puppy food to adult food, depending on his breed.


Size and Age

If your dog is a Chihuahua, he's more apt to live well into his teens. If he's a large dog, such as an Irish wolfhound, his life expectancy is about half as long. Smaller dogs not only live longer as a rule, they also mature quicker in their first few years of life. Large dogs mature slower, yet reach senior status at a younger age, often around 5.


Small and toy dog breeds aren't considered geriatric until they're around 10 years old. Medium-sized breeds are usually around 7 or 8 before they're considered seniors.

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Age Calculation

Whether your dog is small, medium, or large, you can figure by the time he celebrates his second birthday, you're living with a 24-year-old. After his second birthday, your dog's growth rate will vary according to size.


  • Small dogs age four years per year after age two.
  • Medium dogs generally gain five years for every birthday beyond two.
  • Large dogs age six years for every human year.

If your dog is a 6-year-old Chihuahua, she's about 40 in human years, but a 6-year-old golden retriever is closer to 45 in human years. All age calculations and charts are guidelines. Your dog's health and "age" depend on his diet, exercise, and general physical condition.


Estimating Age

If you don't know your dog's birthday and want to get an idea of his age, a good exam can provide clues.

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Teeth are a great indicator of age. Puppies have their permanent teeth by the time they're 7 months old. If a dog has a full set of beautiful white chompers, he's probably about a year old. Slight yellowing on the back teeth begins around age 1-2, and tartar starts building up around 3-5 years of age. If a dog's teeth are worn or missing, she's probably in her senior years, when teeth show the effects of age.


Cloudy eyes, graying hair around the muzzle, face, head and body, and stiffness also indicate senior status. Younger dogs have more muscle definition than older dogs, who tend to be either bony or chubby, depending on their activity level.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.


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