Convert Dog Years to Human Years

The long-accepted dog age rule maintains that every year for your four-legged friend is equal to seven for a human. However, comparing dog years to human years is not that simple. For your convenience we have created this free dog age calculator.

Dog Years To Human Years Calculator

How the 7-to-1 Calculation Began

The dog age equation goes beyond simple mathematics. For example, many dogs reach sexual maturity around 1 year of age, and some even sooner than that. A human child is typically 13 or 14 before reproductive hormones start kicking in.

But with dogs, there are plenty of other factors to consider when it comes to longevity, including the breed of dog. For instance, a Saint Bernard is destined to have a shorter lifespan than the average chihuahua. With all the variables, it seems the theory of comparing dog years to human years can be rendered almost moot.

So, how did this generally accepted dog age calculator get started, anyway?

No one really knows for sure. There is an inscription dated 1268 in the Cosmati pavement in front of the High Altar of Westminster Abbey. The pavement was ordered by Henry III and refers to the end of the world. For some reason, the ancient text states that the health of an 81-year-old human would be equivalent to that of a 9-year-old dog. The vitality of a person that old may have been a guess since many people tended to live only into their 30s in those days.

But the popular 7-to-1 ratio was probably initiated by a 1700s French naturalist, Georges Buffon. The Count de Buffon theorized that since humans lived around 90–100 years and dogs lived 10–12 years, every dog year equaled about seven for a person.

Since then, the dog age calculator has been enshrined in society as dog years to human years equaling one to seven, respectively. The theory was so widely accepted that it was even included in math textbooks beginning in the 1960s.

Although the comparison may be generally accurate for the typical older dog, there are many different factors which prove the traditional dog age calculator to be inaccurate. A few of these include the facts that:

  • 1) Many dogs live past the age of 15, which at the 7-to-1 ratio would put a person at 105. Dogs, in fact, have been known to live over the age of 20 (140 human years), and the oldest dog on record was 29 (or 203 human years). The oldest human, on the other hand, managed to stay around until age 122.
  • 2) A 1-year-old dog is more of an adolescent than a 7-year-old human.



    Dogs and Humans Do Not Age at the Same Rate

    From birth until they reach their adult stage, dogs grow at a far more accelerated pace than humans do. A dog at 2 years of age is similar in maturity to a person in their mid-20s. Upon reaching that stage, a dog’s growth will slow down and level off to about 3–5 dog years for each human year.

    French researcher A. Lebeau created a new calculation for the dog years to human years conundrum. Although that was in 1953, the 1- to 7-year ratio continued to dominate public thinking on the matter, probably because it was simpler in theory. But Lebeau calculated the age equation at a 4:1 ratio following the dog’s second year. However, Lebeau’s method didn’t take into consideration how some dogs reach old age at just 7 or 8 years. So, no known method for a dog age calculator can be truly accurate in the universal sense.


    Dog's age Small breed
    (up to 9 kg)
    Medium breed
    (9 to 22 kg)
    Large breed
    (22 to 44 kg)
    Giant breed
    (above 44 kg)
    1 15 15 14 12
    2 24 24 22 20
    3 28 29 29 28
    4 32 34 34 35
    5 36 38 40 42
    6 40 42 45 50
    7 44 46 50 57
    8 48 51 55 64
    9 52 56 61 71
    10 56 60 66 79
    11 60 65 71 86
    12 64 69 77 93
    13 68 74 82 100
    14 72 78 88 108
    15 76 83 93 115
    16 80 87 99 122
    17 84 92 104 129
    18 88 96 110 137
    19 92 101 115 144
    20 96 105 121 151
    21 100 110 126 158
    22 104 114 132 166
    23 108 119 137 173
    24 112 123 142 180
    25 116 128 148 187


    The Breed of Dog Will Affect Its Life Expectancy

    Thanks to selective breeding, the modern dog has evolved into the world’s most diverse mammal in existence. Dogs can vary in weight from 4 pounds to 200 pounds, and their body style and haircoat show enormous variety.

    The length of the dog’s life tends to depend on its size, which is the opposite of how it usually works for mammals. Large animals, such as horses, live much longer than tiny ones, such as mice. But a large dog will age much more rapidly than a small one. The tall and stately Great Dane will typically live only 6 or 7 years. The tiny, scrappy Yorkshire terrier can live well into its teens.

    Genetics, of course, play a large role in longevity. Hybrid vigor factors in. A pedigreed dog tends to live a shorter life than a mixed breed of the same size, which statistically will have an additional year to stick around. The overall longevity of pedigreed dogs is 12 years. The longest-lived breeds include:

    • Miniature Dachshund
    • Miniature Poodle
    • Bearded Collie
    • Border Collie

    The shortest-lived breeds include:

    • Dogue de Bordeaux
    • Great Dane

    There are, of course, exceptions. The Mongolian Bankhar, a massive guardian of livestock, is known for living into its teens and even early 20s despite maintaining an outdoor lifestyle in a harsh environment.


    Figuring out your dog’s age by human standards can be tricky, especially with so many variables, such as breed, size, and genetic predispositions, like hip dysplasia and other abnormalities. There are free online dog age calculators that can help you figure out the human age approximation of your dog. Enter your dog’s information, click on a button, and your answer will pop up. Just remember not to take it too seriously. Longevity is not an exact science.

    Perhaps the most important thing about the dog age calculator is the fact that it displays how long dogs have played a significant role in the life of mankind. It is a sobering fact to realize that for hundreds — even thousands — of years, people have wondered how long they would enjoy the companionship of a beloved pet. Many of us consider our dogs to be family members, and we want to give them the best life possible. It would be nice to know how much time we have. But the most we can do is figure out the averages and hope for the best.

    Meanwhile, with these canine partners, whether furry or smooth, large or small, with tails that are fluffy or wagging or stubby, we remember their lives are more temporary than our own, and our best option is to make the most of every day.