How to Tell a Dog’s Age: 5 Signs to Look For

Estimating a dog’s age is easiest when they’re puppies in the first weeks and months of life: Dogs go through stages of development like opening their eyes and ears and beginning to walk at roughly the same age. As a pup grows, we can guess their age based on size, weight and breed, too.

Just like humans, older dogs tend to sprout some gray hair, which typically progresses with age. When dogs reach 7-10 years old, they are likely to develop some gray or white on their chest, haunches or muzzle. But gray fur isn’t the only difference you’ll notice in their fur; a lot of times, a dog’s fur color will lighten with age, too.

Be sure to observe your new dog’s fur condition, too. When they are young, a dog typically has a soft, shiny coat thanks to their skin’s hydration levels. But when a dog is older, their fur tends to be drier and weaker. A lackluster coat, compared to the shiny fur you see on younger healthy dogs, is a sign of an older dog.

Are your dog’s eyes clear and lively? If so, it’s likely they are no older than 3 or 4 years old.

That’s because, as dogs age, a bluish, transparent haze develops in the lens of the eye. It’s called nuclear sclerosis, aka lenticular sclerosis, and it’s considered a normal part of aging. It does not affect vision, although vision will worsen a little with age.

Other age-related eye conditions, such as cataracts and glaucoma, can also give dogs cloudy eyes or a bluish discoloration of the pupil. These conditions do affect dogs’ vision and require treatment from a veterinarian.

A dog’s energy level can vary widely from one day to the next, and it’s not just dependent on age. Keep the 3-3-3 rule in mind when you adopt a new dog: Most pups spend three days of feeling overwhelmed and nervous in a new home, followed by three weeks of settling in, and three months to build trust and bond with you. This—as well as any illness acquired from the shelter or street life—can affect their energy levels in a big way.

But once your pup has reached three months in your care, you can more properly assess how energetic they really are. Puppies and younger (up to age 2) dogs tend to be filled with endless energy and will play for hours before tuckering out. Older dogs, on the other hand, are less energetic and playful; they also need a lot more sleep compared to younger adult dogs. Older dogs often become stiff and slow, particularly larger breeds, and many senior dogs will experience some degree of canine dementia, which can lead to confusion and lethargy.

A dog’s breed has a real impact on how quickly they age, as well as their lifespan. For example, “an 8-year-old Chihuahua will be energetic and may look quite similar to a 3-year-old Chihuahua,” says Simon. “Conversely, an 8-year-old Great Dane will be coming to the end of their life and will likely be experiencing chronic health issues such as arthritis. It will be evident from their appearance that they are a senior dog.”

Don’t know your dog’s breed or mix of breeds? The same rule generally applies to a dog’s size: Small dogs tend to live longer, and therefore age more slowly, while larger dogs tend to have a shorter lifespan, aging faster.

How to Tell Your Dog’s Age in Human Years

We’ve all been told to multiply your dog’s age by seven to calculate how old they are in human years. But what if we told you that is entirely wrong? The American Kennel Club (AKC) says the long-believed “one dog year equals seven human years” theory is not supported by science.

There’s more to identifying our dog’s human age than simply multiplying their age by seven: As we explained above, factors like physical and mental development, as well as breed, affect your dog’s true age. A Great Dane will not age in the same manner as a Chihuahua, and an outdoor working dog will age faster than an indoor pup. An overweight dog will age quicker and develop more health conditions compared to a dog who is at a healthy weight. Use our age calculator chart that takes some of the guesswork out of that math for you.