Dog Age in Human Years Calculator

Calculate how old your dog is in human years, using 3 methods of canine aging: dog age based on size, with the epigenetic clock study formula, and using the 7 year rule (obsolete, but interesting for comparison). More info on each method below.

How old is a 3 year old dog in human years?


Dog's Age in Years

Based on dog's weight: each size shown in pounds and kilograms

(Optional)

More: Cat Age Calculator, Human to Dog Age Converter

Entry Fields

In the Dog's Age field, enter the age, in years, of the dog for whom you are calculating.

Specify the Dog's Size by selecting from the drop down list. The available sizes are:

  • Small - select for dogs which weigh less than or equal to 20 pounds (lbs) or 9.1 kilograms (kg).

  • Medium - select for dogs which weigh between 21 to 50 lbs (9.2 to 22.7kg).

  • Large - select for dogs weighing between 51 to 100 lbs (22.8 to 45.4kg).

  • Very Large - dogs which weigh over 100 lbs (45.4kg).

Note: this field is only used for dog aging based on size; However, as the dog age calculator performs all three aging formulas, this field is required.

Maximum dog age is 32 years old. It's rare for a dog to live over 18 to 20 years, but there have been some older dogs. So that you can what-if calculate in case your dog lives a long life, we've provided up to 32 years. With scientific breakthroughs extending longevity of both people and dogs, who's to say what's around the corner!

Bobi, Oldest Dog

The oldest recorded dog is Bobi from Portugal. Bobi turned 31 in 2023 according to Guiness World Records.

In late October, 2023, at age 31.5 years old, Bobi died at his home in Portugal. It's likely Bobi will remain the world's oldest dog on record for some time, since the runner-up, Bluey, an Australian Cattle Dog who who died in 1939, was 29 years and 5 months.

Follow-up on Bobi

January 2024 - Bobi-Gate
Bobi's title as World's Oldest Dog has been suspended by the Guiness World Records, pending further investigation. Some journalists decided to dig up some dirt on Bobi, which, in turn, resulted in not only his suspension, but also, temporarily, runners up. Doggonit!

February 22, 2024 - Bobi's out as world's oldest dog
The investigation did not go well for Bobi, and the Guiness World Records has rescinded his title of being the world's oldest dog, finding no evidence that he was, in fact, 31 years old. Oh woof to that! Read more about Bobi's revocation at Reuters.com and see his cute photo!

About Dog to Human Age Calculator

Since dogs pass through life so much more quickly than people, it's only natural to want to know how old one's dog is in comparison to our own human age. This correlation is also important as our dogs age, since dogs are afflicted by many of the same health issues and illnesses as occur as humans age, from hearing loss to arthritis to diabetes.

This calculator uses three different methods to calculate approximately how old your dog is in human years:

  1. Dog Age Times 7 Years - To calculate your dog's age, her chronological age is multiplied by 7 years to arrive at her people age. That is, each year of a dog's life is equal to about 7 human years. So, if your dog is 2 years old, his human age would be 14 years; If 4, he'd be 28 human years.

    This equation, which came into usage in the middle of the 20th century, may have been devised to parallel human life expectancy, which, at that time, was about 70 years old in the USA and many European countries. Consequently, if one's dog lived to 10 years old in 1950, its lifespan was 70 years (10 x 7), just like her human family's.

    Here in the 2020s, the Times 7 Years calculation is largely dismissed: it is not backed by veterinary science; Moreover, human life expectancy has increased, so the 1 to 7 correlation no longer holds.

  2. Age by Dog Size - A fundamental flaw to the Times 7 rule is that it assumes all dogs age at the same pace, and this has been shown to be false. A dog's size, as measured by its weight, plays a more significant role in how quickly it ages.

    In general, smaller dogs live longer than larger ones. For example, a Chihuahua, which weighs about 6 pounds, has a lifespan of 14 to 16 years, whereas a German Shepherd, which can weigh 10 to 15 times that, depending on gender, has a lifespan of 7 to 10 years.

    Information about dog longevity is compiled by several entities: organizations specializing on dog breeds, such as the American Kennel Club (AKC); companies providing pet insurance; and veterinarian organizations/hospitals. Ultimately, what the extensive datasets show is that dogs in a specific size group (small, medium, large and very large) age at a similar rate.

    Over the first 2 years, dogs age quickly, the equivalent of about 15 human years the first year, and 9 more human years by age 2. After that, each additional year of a dog's life is equivalent to between 4 to 6 human years, depending on size, with smaller dogs aging more slowly (about 4 human years per 1 dog year) and larger dogs aging more quickly (about 5 to 6 years per 1 dog year).

    Currently, aging by dog size is considered to be more accurate, as it is based on actual data aggregated from large datasets.

  3. Epigenetic Clock Study - In 2019, a study at University of California San Diego used an epigenetic clock, which is a biochemical test, to measure and compare aging based on DNA methylization in both humans and dogs. From this study, the researchers derived a formula for converting a dog's age to its human age:

    16 * natural logarithm (dog's age) + 31

    What the study found, as shown by applying the formula, is that dogs age rapidly in terms of human years until they are about 4 dog years old, after which their aging slows down dramatically for each additional dog year.

    Keep in mind that the study was limited: only 104 dogs participated, ranging in dog age from 4 months to 16 years. And, the dogs were all of the same breed, labrador retrievers. It will be interesting to see if future studies are run on a wider variety of dogs and if the formula sustains.

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