How to determine my dog’s age in human years

By Kristia Goodnight

Many dog owners, especially owners of rescue dogs, are curious about the age of their dog. Dog owners may have an approximate age of their dog based on the rescue or shelter's estimations but calculating the exact age of a dog can be difficult.

The 1 human year equals 7 dog years ratio

The most common advice to calculate how old is your dog in human years is that 1 human year equals 7 dog years. This is actually a myth!

Popularized in the 1950s, this misconception was an overgeneralized statement based on assumptions of average human and dog lifespans. At the time, the average human lifespan was around seventy years and the average dog lived about ten years.

Surprisingly, new research has shown that there is no direct ratio of how many dog years are in a human year. Meaning you can’t convert human years to dog years to find out a dog’s age.

Dogs age more quickly in their first years of life and then even out throughout adult life until becoming a senior dog.

How to tell how old my dog is?

While there is no perfect dog age calculator, the American Veterinary Medical Association has determined general guidelines to calculate how old is your dog in human years:

The first year of a medium-sized dog’s life equates to about 15 human years.
Year two for a dog equals about nine additional human years, making the dog about 24 in ‘dog years’.
After age two, each human year adds around five dog years.

Most dogs are considered puppies until their bones have fully developed and they’re fully grown. Usually between the ages of one to two years. From there, a dog is an ‘adult’ until they reach senior status.

Small breed dogs (under 20 lbs.) are considered seniors after the age of seven or eight. Large and giant breed dogs can reach senior status as early as five or six years of age. Knowing when a dog is reaching the senior age category can help owners better anticipate the changes in care their dog may need.

How old is my dog in human years? How to find out a dog's age

The best way to find out the accurate age ofhow old is your rescue or shelter dog is to get your dog’s microchip scanned at a veterinary clinic or shelter. The information stored in your dogs’ microchip may reveal the original breeder or owner of the pet, who may have details about your dog’s age, plus medical history, and other important information.

However, many dogs arrive at shelters without a microchip or their owner’s information isn’t registered, making it impossible to find out how old the dog is.

In this case, a veterinarian can provide you with a rough estimate based on one of your dog’s physical characteristics, their teeth. Especially useful in determining the age of younger dogs, dog’s teeth can reveal a lot about their general age.

8 weeks

All 28 puppy baby teeth have come in.

4 months

Baby teeth begin to fall out and adult teeth can be seen coming in.

7 months

All 42 permanent teeth are in. Teeth appear clean and bright.

1-2 years

Overall, teeth appear more dull and back teeth may show signs of yellowing.

3-5 years

All teeth may show tartar buildup and general tooth wear. Nearly 80% of dogs will show signs of gum disease like buildup of yellow and brown tartar, inflamed gums, and bad breath by age three.

5-10 years

Teeth show significant wear and may show signs of gum disease.

10-15 years

All teeth will be noticeably worn with heavy tartar buildup likely if regular dental care is neglected. The dog may be missing some teeth.

Senior dogs may also show other physical signs of aging like graying fur, stiff joints, small fatty lumps on their bodies (called lipomas), general slowing down, and behavioral changes.

Click here to view PDF of full chart

How long do dogs live in human years?

Studies show that dog breed and size greatly impact the average lifespan of dogs. Generally smaller dog breeds have a longer average lifespan than larger dog breeds.

Researchers are still studying why large breed dogs age faster when compared to smaller breeds. One possibility is that because they age more quickly, large dogs may succumb to age-related illnesses sooner.

Another factor is the differences in the specific types of medical conditions that affect different-sized breeds.

Lastly, genetics are a major factor when determining life expectancy for dogs. Some breeds have higher rates of hereditary illnesses and proclivity for certain medical conditions due to limited genetic variability in parent generations.

Many mixed-breed dogs have more genetic variability, which can reduce the risk of hereditary diseases.

Small-breed dogs, like Pomeranians and Yorkies generally have the longest lifespans, averaging 10-15 years.
Medium-size dogs, like Cocker Spaniels and Boxers have an average dog lifespan of 10-13 years.
Large-breed dogs like Golden Retrievers and Labs tend to have shorter life span ranges averaging 9-12 years.
Giant-breed dogs like Great Danes and Saint Bernards have the shortest average lifespan, at 8-10 years.

Remember that dog lifespans are general averages and individual dogs may or may not have a general experience. In fact, according to Guinness World Records, Bobi, a purebred Rafeiro do Alentejo, a Portuguese breed of livestock guardian dog from Spain is 30 years old, and the oldest dog verified.

Caring for your dog at every age, from puppy to senior dog

One way to give your dogs the best care is knowing how old your dog is. Although visiting the veterinarian every 6 to 12 months is recommended to keep your dog healthy regardless of their age, they might need more frequent check-ups or receive different treatments based on the life stage they are in.

Puppies will make more frequent visits to get their vaccines, deworming, and monitor their growth. They may get spayed or neutered at this stage too.

As a young adult, your dog will receive appropriate protection against fleas, ticks, and heartworms. They will also be monitored for healthy weight and dental wellness.

As our dogs age they require extra care and patience. Senior dogs may experience unseen challenges like arthritis, loss of sight and hearing abilities, diminished mental capabilities, among others.

Caring for your senior dog can include increased visits to the vet to monitor signs of illnesses or to catch and treat medical conditions early.

Ultimately, the frequency of visits to your veterinarian will depend on your dog’s health throughout their entire life and if any pet health emergencies come up.

How to help your dog live longer

Trust your vet: Following your veterinarian’s advice on routine and preventative health care like vaccinations and parasite prevention can protect your dog from preventable illnesses and health issues.

Keep Your Dog Healthy: Feeding your dog high quality food and maintaining a healthy weight can add years to your dog’s life. A 2019 study found that dogs kept at a healthy weight lived an average of two years longer than their overweight counterparts.

Maintain Dental Health: Veterinarians estimate that 80% of dogs aged three and up suffer with dental disease. Periodontal disease can lead to inflammation and damage to their vital organs. Prioritize annual dental exams and at-home dental care tools like dental chews and water additives that protect against dental disease.

Research: If adopting a purebred dog, choose a responsible breeder that tests for common breed specific diseases and is invested in the health and genetics of their dogs.

If adopting a dog from a rescue or shelter, consider a dog DNA to find out your dog’s genetic makeup and even markers that your dog may have for the genes for common diseases. Better understanding your dog’s unique genetics can help you anticipate potential health concerns that may arise.

Calculating a dog’s age in human years

Learning the specifics of a dog’s age by checking their microchip information or their physical characteristics can help dog owners to better care for their dog during every stage of life from puppyhood to senior dog; and even help their dog live a longer and healthier life.