How To Determine A Dog’s Age

Part science, part artful guesswork
By Karen B. London PhD, April 2019

“How old do you think my dog is?”

It’s so natural for guardians to ask this question, but it is equally natural for veterinarians to dread having to answer it. While it is a simple query, it is decidedly complex to offer a reliable response. There are a number of clues that can be used to estimate a dog’s age, but unless the dog is still a puppy, the accuracy of the guess may be anywhere from close to the truth to wildly off.

Teeth. Puppies have baby teeth which fall out and are replaced in a fairly predictable, age-dependent pattern, so very young dogs can typically be aged accurately by examining their teeth. Most dogs will have all of their adult teeth in by the time they are about six months old, and once that happens, the teeth offer less exact information about age. Generally, the condition of the teeth will change with age and have more tartar, wear and tear, and gum disease. However, factors such as diet, chewing habits and genetics all have such a large influence that it is not unusual to see a young dog with teeth in poor condition or an old dog with relatively healthy teeth.

Lens Clarity. Middle-aged and senior dogs often have a haze on the lenses of their eyes. It makes the eyes look a little blue or cloudy. This haziness is called lenticular sclerosis and does not change the transparency of the eye to light and doesn’t affect vision like cataracts do. It is a normal change in dogs’ eyes as they age and usually occurs in both eyes. About half of all dogs will show this condition by the age of 9 and within a few more years, it’s present in almost every dog.

General Body Condition. The distribution of a dog’s weight changes with age. Older dogs will often have fat pads in their lower back area. Loss of muscle occurs as dogs get older, too. A prominent spine and a swayback indicate that a dog is more of a senior citizen than a spring chicken.

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Graying Fur. Graying around the muzzle and eyes certainly makes dogs look older, but this sign of age is not as useful as we might wish. Many dogs start to get that distinguished silvery look when they are only a few years old, and some senior dogs still have their original color.

Changes In Overall Appearance. If you’ve adopted an adult dog, an age estimate may not be super accurate, but as time goes on, you might be able to improve your guess. If you’ve had an adult dog for several years and any changes in general appearance are minimal, your dog was probably pretty young when adopted, perhaps two, three or four years old at the time. Medium and large dogs from age two to eight can be remarkably similar in appearance so it’s only as they age out of that range that that it’s easier to determine when they were born. Smaller dogs who have not changed in several years have a wider starting age range—perhaps from one to five years at adoption.

The length of time you’ve had your dog. Besides the physical appearance of your dog, one major clue about age is how long you have had your dog, so your veterinarian will probably ask you that just to determine a starting point. (If you’ve had your dog for three years, your dog can’t be only two years old!)

There is a very good chance that if you’ve asked a veterinarian to guess your dog’s age that you found the answer unsatisfying. There is just too much guesswork for accuracy to prevail. If you adopted a dog of unknown age, how confident are you that you know how old he or she is?

Karen B. London, PhD, is a Certified Applied Animal Behaviorist and Certified Professional Dog Trainer who specializes in working with dogs with serious behavioral problems, including aggression. She has authored five books on canine training and behavior.

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