What Are Dog Years?

(Last Updated On: August 31, 2020)

What Are Dog Years?

If you’ve ever been anywhere near a dog you’ve also been near the concept of “dog years.” More or less, it’s how we dumb humans scale dog ages to be relative to ours so we can rationalize the way dogs age. So what are dog years anyway? Also, how are we probably wrong about them?

The Old Ways

Conventional wisdom has led us to assume dogs age about 7 years (relative to us) over the course of 1 year. Which is a really long way of saying “dogs age exactly 7 times faster than us.” 

Nobody actually knows where this old rule came from. Though this kind of “linear scaling for dog age” has been around for a really long time–at least as far back as 1268. An inscription at Westminster Abbey from back then detailed dog years basically being 9 to 1–also known as  humans live up to 81 years, where dogs live to 9. There have been a couple other rules as well–basically just taking the age of humans divided by the age of dogs.

By the mid 1900s, the general consensus of the 70 year human lifespan took hold. Dogs were believed to average about 10 years. This is probably where the 7 to 1 ratio for contemporary dog years comes up. Some think it was hugely boosted by veterinary marketing.

But honestly, the 7 to 1 dog year probably took hold because it’s super easy. If you take the maximum lifespan of a human divided by the maximum lifespan of a dog, you can very easily scale the age of your pet to your own. It’s a lot easier to just multiply your dog’s age by 7 to get insight into their development than it is to pull out calculators and blood tests and scales or whatever other tools you could use.

It’s a nice shorthand.

The New Age

Well… Your dog doesn’t have a new age. Your furry friend is still however many years old in real-time.

But it turns out multiplying your dog’s age by an arbitrary number is actually a relatively pointless overgeneralization. It assumes that dogs age the same way we do, which is quite anthropocentric and also untrue. 

Obviously animals don’t age the same way we do–if you’ve ever seen animals born in the wild on documentaries you’ve probably seen newborn deer or giraffes begin walking immediately. If giraffe age averages to about 25 years, and the average human lifespan is about 80 years, then one giraffe year is about 3.2 (we’ll say 3) human years. Since humans start walking (on average) at about age 1, a giraffe wouldn’t know how to walk until it was about 4 months old if we assumed they aged like we do.

Obviously, giraffes don’t take 4 months to learn how to walk, the lions would have long since gotten them.

While obviously that math is a bit of an overgeneralization (just like dog years), humans are simply born less developed than many other animals to support our proportionally big heads. 

But, the point is not everything ages in the exact same way we do, and dogs are no exception.

So How Do Dogs Age?

The speed at which dogs age actually depends on how much they weigh, and perhaps strangely, how old they are.

Because dogs don’t age in a way directly proportional to us humans, they age at “different speeds” if we were to try comparing them directly to us. Heavier dogs, on average, age “faster,” a 50+ pound dog is considered geriatric at age 7, but a dog less than 20 pounds gains geriatric status at age 11. 

Of course this also depends on your dog’s breed, pugs and bulldogs are far more prone to age-related complications (and other complications in general)–stuff like that. 

Dogs also “age” much faster early on in their lives. Honestly, because we use “age” as a catchall to refer to dog development, it’s probably easier to think about it that way. 

A 1 year old dog might be as developed (proportionally) as a 12-15 year old human depending on their breed. That’s right, your good boy actually has some sick wisdom to drop on you a lot earlier than you think. Dogs don’t continue this rapid development, though, by age 6 they’re probably more around 40 (using a linear scale they’d be over 60). If you were to plot a line of how old your dog was using human years as a scale, humans would quite intuitively age in a line. The dog’s age would be curved. Here’s a study with more math.

Go say hi to your pet, and give them a treat for us.

I’m not sure how my boy has aged, but I’m pretty sure it’s wrong.

Like puppies? Here are some really young dogs that you now know are a little older than they might seem.



About Kyler 728 Articles
Kyler is a content writer at Sporcle living in Seattle, and is currently studying at the University of Washington School of Law. He's been writing for Sporcle since 2019; sometimes the blog is an excellent platform to answer random personal questions he has about the world. Most of his free time is spent drinking black coffee like water.