It’s normal for pet parents to worry about their canine companion’s longevity. That’s why the question ‘How long is a dog year?’ remains popular to this day. Over the years, humans have devised various methods to gauge canine aging, including calculating the dog’s age in human years. That’s where the 7-year dog rule, or the rule of thumb for calculating a dog’s age in human years, comes from.

But is 1 dog year really equal to 7 human years? Modern science has almost done away with the 7-year myth. Why? That’s what we’re here to explain, including how to use a dog age calculator.

This article will highlight all facets of canine maturity, how calculating dog years – or more specifically a dog’s age in human years – has evolved, and the latest advancements. Stay with us as we simplify the challenges of measuring dog years and how to best care for our furry friends, no matter their stage of life.

Table of contents

Historical Context of the 7-Year Myth

There have always been myths about dog years. Many generations of pet owners grew up thinking that one dog year equals seven human years. The 7-year rule-of-paw dominated the concept of dog aging for years. But no one knows exactly where it comes from.

Decoding the Origins of the Dog Rule

When determining a dog’s age in human years, experts offer two possible explanations. One, the rule was developed by canine enthusiasts trying to figure out a simple scale for calculating dog age. Regardless of the dog’s size, when the dogs age much compared to humans – the comparison went like this – dogs live 10 years compared to the average human life expectancy of 70 years. Hence the 1:7 ratio.

The other justification links to the ‘Doomsday’ etchings in Westminster Abbey. Whoever came up with the Judgement Day estimates measured canine lifespan to equal nine years.

Historians deduce that the original 9-year cycle was reduced to seven years eventually to reflect the diminishing life spans of all living things.

While the math involved in the ‘dog year’ estimate isn’t sound, the rule persisted until quite recently. That’s probably because it gave dog owners some understanding of how their pets aged and the level of care required at different stages of life.

Understanding Dog Aging: How Fast Do Canines Age?

Data collection and analysis, especially in areas concerning how old your dog is in human years, has improved dramatically. That’s one significant reason why associations like the American Kennel Club (AKC) and the American Veterinary Medical Association (AVMA) use aggregate data to arrive at factual statistics about how dogs age.

Here’s what 1 dog year in human years looks like.

As per the guideline generated by the AVMA:

  • One year of a medium-sized canine equals about 15 human years.
  • When using a dog age chart or years calculator, you find that the second year of a dog’s life equals approximately nine human years.
  • Year three and onwards, each dog year equals five human years.

These estimates from dog age calculator reveal that our small dogs tend to age rapidly in their first year of life. The aging of a dog in human years slows down from year two onwards. But before you reach for your calculators, there’s something else you should know.

Since large canine breeds have shorter lifespans compared to smaller breeds, how fast a dog ages can vary based on size. The AVMA breaks down canine seniority in the following manner:

  • Giant breeds weighing more than 90 pounds become seniors at six to seven years of age
  • Large breeds weighing 50-90 pounds become seniors at eight to nine years of age
  • Medium breeds weighing 20-50 pounds become seniors at eight to ten years of age
  • Small breeds weighing less than 20 pounds become seniors at eight to eleven years of age

If you’re wondering, ‘do larger dogs age faster than smaller breeds?’ the answer’s yes! A study in The American Naturalist proposes that the fast development larger canine breeds experience can burden their physiological processes, leading to accelerated wear and tear.

A More Accurate Conversion: Breaking Down Dog DNA

Looking for a more scientific approach to the question ‘How to calculate dog age?’, then you might want to pay attention here. While the estimates provided by the AVMA aren’t inaccurate, they’re based on empirical evidence rather than scientific evidence. In short, they leave room for mistakes.

Scientists from the University of California, San Diego, and other equally respected institutions got together to investigate the methylation patterns in the DNA of 104 Labrador Retrievers aged four weeks to 16 years.

Without getting too technical, methylation can help reveal biological age acceleration. So, the scientists tracked canine methylation and compared the data with similar patterns in human beings.

The information revealed the first eight weeks of a canine’s life aligned to approximately nine months in humans. Moreover, the data showed humans and dogs have average life expectancies of 70 and 12 years, respectively.

The study’s results allowed researchers to determine the following formula to adjust canine ages to human years: human age = 16 ln(dog age) + 31.

If numbers aren’t your strong suit, you can scroll down to the table below to compare human and dog years according to this study.

Dog Age Conversion Chart

Human AgeDog Age
9 Months8 Weeks
1-12 Years2-6 Months
12-25 Years6 Months – 2 Years; Critical Period for Calculating Dog Years to Humans
25-50 Years2-7 Years
70 Years7-12 Years

Dog Age Conversion Chart

Dog enthusiasts should note that the UCSD formula, which calculates dog age in human years, may be state-of-the-art, but there’s still a margin of error since the study was based on a single breed of dog.

Why Size Matters – Dog Lifespan by Breed and Size

A dog’s lifespan can be affected by its breed and size. Smaller canines have longer lifespans, often reaching 12-16 years. Conversely, large dog breeds have shorter lifespans, typically around 8-12 years.

This size-related difference is due to the physiological and genetic variations between breeds. Smaller dogs age slower and experience fewer health issues, whereas larger dogs age rapidly and are susceptible to age-related illnesses.

Here’s how these facts translate to average lifespans among canines of various breeds and sizes.

Breed (size)Average Lifespan
Chihuahua (small)14-16 Years – Equivalent Dog Age in Human Terms
Cardigan Welsh Corgi (small)12-14 Years – Indicative of Advanced Dog Age in Human Terms
Dalmatian (medium)12-14 Years
Border Collie (medium)10-13 Years
German Shepherd (large)10-12 Years
Saint Bernard (giant)Utilizing the dog years to human years calculator, how old would a small dog be in human years when it is 8-10 dog years?

Dog Lifespan by Breed and Size Toy poodle babies

How to help your dog live longer?

Health and lifestyle can seriously impact your pet’s aging process. For example, dogs benefit from a nutritious diet, regular exercise, and proper medical care.

Small dogs, particularly those of a specific breed of dog, with wholesome habits tend to age better, retain muscle mass, and have fewer joint problems. They also tend to live longer than larger dogs. On the flip side, an inactive lifestyle, seclusion, and poor nutrition can accelerate aging, leading to obesity, heart disease, and arthritis.

Research by the Dog Aging Project examines human and dog DNA to determine dog age in human years. reveals that canines with a robust social network age healthier. So, how your pet lives matters. Finally, preventative healthcare, like vaccinations and regular check-ups, can detect health issues early and help extend a pet’s quality of life.

Why Dog to Human Years Conversations Matter

Why do we convert dog years to human years? That’s straightforward. Understanding the basics of canine aging can help pet owners break down caretaking and tailor it to their pet’s life stage.

Things like nutrition, exercise, and medical attention can vary according to your canine’s age group. Pups require intensive care in terms of diet and veterinary check-ups. The same is true for senior dogs.

Besides that, dog year conversions can help you build a deeper bond with your pet. You can empathize with the age-related changes your dog is going through and become a responsible and proactive pet parent.


The 7-year dog rule has been redundant by better methods of measuring dog lifespan by breed and size. Be it AVMA’s guidelines or UCSD’s methylation-based formula, calculating your pet’s age has become much easier.

But it’s important to note that these calculations are estimations, not gospel. Your pet’s breed, size, and lifestyle can impact its longevity.

As a dog parent, you need to focus on providing your canine with a nutritious, vet-approved diet, optimal exercise, and social bonds for overall health. Let’s not forget to stick to those vet appointments like clockwork.

Do all this, and we’re sure you’ll be well on your way to improving your canine’s lifespan.


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