How Do Dog Years Really Work?

For some time, dog owners have believed that one human year encompasses seven dog years. It’s obvious to dog owners that their precious pups age much faster than humans, and at some point in the 1950s, someone started the rumor that one human year equals seven dog years. However, that actually is not the case.

The truth is, calculating dog years is much more complicated than simply multiplying a human age by seven. Dogs actually have some of the greatest variabilities in aging based on breed and size among all animal species. Therefore, it’s difficult to know exactly how to calculate a dog’s age.

Calculating Your Dog’s Age

Every dog is different, so it’s not entirely possible to calculate your dog’s age accurately. However, there are some general guidelines you can follow that may help you guess your dog’s age rightly.

Here’s a quick and simple guide:

The first year of your dog’s life encompasses about 15 years of growth as measured in human years.
The second year of your dog’s life encompasses something like 9 years of growth in human terms.
Every consecutive year of your dog’s life encompasses about 4 or 5 human years.

Of course, as mentioned, this is going to differ for each dog. For whatever reason, bigger dogs age more quickly than smaller dogs, which means that your Great Dane will likely live only seven to ten years, while your Miniature Pinscher might live more like 15 years.

Based on a chart developed by scientists during a 1997 study, you can expect your dog to follow an aging pattern that looks something like this:

Chronological Age	Age in “human years” based on weight
	15 to 30 pounds	30 to 50 pounds	50 to 75 pounds	75 to 100 pounds	100 pounds or more
1	12	12	14	16	20
2	18	19	21	22	26
3	24	25	26	28	31
4	30	30	32	34	37
5	35	35	37	39	42
6	38	40	42	44	47
7	44	44	46	48	52
8	48	48	50	52	56
9	51	51	54	57	61
10	55	56	58	61	66
11	58	59	62	66	71
12	62	63	66	70	77
13	65	67	71	75	83
14	69	71	75	80	89
15	73	75	80	86	96

Checking Age on a Stray or Unknown Dog

If you pick up a dog from the side of the road or a pound or somewhere where their age is entirely uncertain, it’s possible to calculate the age based on teeth. All dogs get their baby teeth in by about eight weeks, so if your dog has all their baby (deciduous) teeth but nothing bigger, it’s likely that they’re not much older than eight weeks.

Now, if your dog appears to have all their permanent teeth in and those teeth still look white, clean, and new, then it’s possible that they are closer to seven months, as this is when most dogs will get their full set of permanent teeth.

Once your dog reaches one or two, their teeth will start to dull and look a bit yellow. By three years and up to five years, your dog will likely have some wear and tear as well as significant tartar buildup. Between five and ten years, expect more wearing and some signs of disease; by ten to fifteen years, you’ll likely see heavy tartar buildup and possibly missing teeth.

In addition to using teeth to guess age, you could also take your dog to the vet for a full physical exam. In general, if their fur is graying (especially around the face), their eyes are cloudy, their skin is a bit loose, and their legs are stiff, they are probably pretty old. Your vet can look at skeletal structure, organ health, and other factors to determine your dog’s age.

Keep in mind that these are all human or chronological years for dogs. If you can guess their approximate human age based on their teeth, you can guess their approximate age in dog years based on the charts provided above.

Why Does Your Dog’s Age Matter?

Besides satisfying your own curiosity, why should it matter how old your dog is? Well, there are a few obvious reasons, if you think about it.

For one thing, it’s important to help your dog stay healthy throughout their life. While vaccine schedules are set for dogs based on human months/years, other health factors may vary considerably based on a dog’s breed and specific age.

For example, if you have a larger dog, you will need to consider them senior by the time they’re about seven in human years. But if you have a smaller dog, they may not technically be senior until they’re closer to nine or ten in human years.

If you’re keeping a close eye on your dog’s diet and exercise habits—as you should be—you’ll want to know their age so that you can support them as they get older and need different types of food or exercise to keep them in prime condition for each age.

As dogs age, the risk for various diseases increases. It’s important that you and your vet work in tandem to provide your dog with all the support they need to stay healthy and, if at all possible, avoid getting severe diseases. At the very least, you will want to help your dog have the most comfortable senior life possible.

Once your dog reaches about seven in human years, it’s a good idea to take them into a vet at least twice a year to get checkups and blood work done. A few other steps to take to keep your dog healthy as they age include:

Feed them a healthy diet with all the nutrients they need—these can change significantly as your dog gets older and loses some of their youthful vigor.
Provide plenty of exercise.
Keep their environment clean and ready for play or rest.
Offer treats, toys, and daily quality time to keep their spirits up.

By following these steps, you can give your dog a happy, healthy life for as many years as they may live!

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