Calculating a Dog's Age

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It's common knowledge that dogs age faster than people. But the conventional wisdom that one dog year equals seven human years is an oversimplified view of how old your dog is in human years. Although a dog's age averages out this way, there is quite a bit of variation. For example, dogs mature more quickly than children in the first couple of years. So the first year of a dog's life is equal to about 15 human years, rather than seven.

Size and breed also influence the rate at which a dog ages. Although smaller dogs tend to live longer than larger dogs, they may mature more quickly in the first few years of life. A large dog may mature more slowly at first but already be considered elderly at age five. Small and toy breeds don't become "seniors" until around age 10. Medium-sized breeds are somewhere in the middle in terms of maturation and lifespan.

In the chart below, use these general ranges for dog size:

• Small dog = 20 pounds or less
• Medium dog = 21–50 pounds
• Large dog = More than 50 pounds

Translating Dog Years into Human Years

How to Determine a Dog's Age

If you've adopted a puppy or dog but don't know the dog's history, you may wonder how old your dog is. Even if you don't know the birth date, it is still possible to estimate your dog's age.

Teeth can give a rough indication of a dog's age. The degree of growth helps determine how old a puppy is, and the degree of wear and tartar helps estimate the age of an adult dog. Of course, there are individual differences between dogs. And a dog's previous dental care will have an impact on the health of teeth.

Here are some general guidelines:

• By 8 weeks: All baby teeth are in.
• By 7 months: All permanent teeth are in and are white and clean.
• By 1–2 years: Teeth are duller and the back teeth may have some yellowing.
• By 3–5 years: All teeth may have tartar build-up and some tooth wear.
• By 5–10 years: Teeth show more wear and signs of disease.
• By 10–15 years: Teeth are worn, and heavy tartar build-up is likely with the possibility of some teeth missing.

Your vet can also estimate your dog's age based on a complete physical exam or tests looking at bones, joints, muscles, and internal organs. In older dogs, signs of aging may show up in a variety of ways, including:

• A cloudy appearance in the eyes
• Graying hair, especially around the muzzle at first, and spreading to other areas of the face, head, and body
• Less skin elasticity
• Stiffness

SOURCES:

AVMA: "Frequently Asked Questions about caring for an older pet."

Purina: "Your Dog's Age in Human Years" and "Caring For Your Older Dog."

National Pet Wellness Month: "Pet Age Calculator" and "Pet Aging Chart."

Humane Society: "How to Determine a Cat's or Dog's Age."

Reviewed by Audrey Cook, BVM&S on March 17, 2010

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