The essentials
- The 7:1 ratio is flawed — That old rule of thumb that one dog year equals seven human years is based on the notion that dogs live about 10 years and humans live to about 70.
- There isn’t a perfect formula — A dog age calculator can give you a better idea of your dog’s age in human years. For parents of rescue dogs who may not know their pet’s birth date, read on for other ways to estimate their age.
- Small dogs typically live longer than big dogs — Small breeds have a life expectancy of 12-15 years, while a larger dog’s lifespan is typically between 8 and 10 years.
There’s nothing cuter than plopping a party hat on your dog and treating them to a dog-friendly cake on their birthday, especially since they have no idea why they’re getting such special treatment. It’s no secret that a dog’s lifespan is significantly shorter than humans, so it’s nice to cherish these milestones while our pups are still with us.
But how exactly does their age equate to human years? You may have heard the rule to multiply their age by seven, but recent studies have found this method to be outdated. Take our dog age calculator for a better approximation of their life stage.
How to use our dog age calculator
To find your dog’s approximate “human” age, select their weight, breed, and years since birth, below. You don’t have to know their exact breed, but it helps to know whether your canine is small, medium, or large because their size and life expectancy go hand-in-hand. For example, the life expectancy of a Chihuahua ranges between 14 and 16 years compared to 11 to 13 years for a Fox Red Labrador Retriever.
The math: how we calculate a dog's age in human years
For the last half-century, many assumed that every year of a dog’s life equaled seven human years. While that formula might provide a rough estimate, it was never scientifically proven and often didn’t make much sense. Using the old method, a 15-year-old dog would be well over 100, while a 2-year-old adult dog healthily capable of producing a litter of pups would only be 14. There’s also the 15-9-5 rule, which sees a dog aging 15 years their first year, 9 years their second year, 5 years every year after. This however doesn’t take breed size into account, which causes discrepancies.
A new way to calculate dog age
A 2020 study suggests there’s now a better way to calculate your dog’s age. A team of researchers at the University of California, San Diego, studied the methylation in a dog’s DNA to see how it corresponds to aging. Methylation in genes acts like “wrinkles,” similar to wrinkles on our foreheads as we grow older. By comparing the methylation of over 100 Labradors to methylation in humans and mice, scientists created a formula to estimate your dog’s age in human years. This new equation multiplies the natural logarithm of the dog’s age by 16 and adds 31.
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Other ways to calculate your dog's age
Perhaps you adopted your dog with no background history, so you don’t know their birthday or even the year they were born. While there’s no way to get an exact number, there are a couple of ways that you can estimate your dog’s approximate age.
Teeth health
Puppies receive all of their baby teeth by the time they’re 6 weeks old. They’ll lose their baby incisors around 4 months, followed by their canines. All of their baby teeth are gone by 6 months, replaced by 42 permanent teeth. If you’ve adopted a puppy, you’ll either notice the thinner, sharper pricks of baby teeth, missing teeth, or new adult teeth beginning to fill in the gaps. During their first year, a dog’s teeth should also appear fairly white.
By their first birthday, your dog’s canines may already be turning yellow. Usually, dogs will have developed periodontal disease by the time they’re 3, depending on their diet and oral hygiene plan.
Coat color
The presence of gray hair may give you a hint of your dog’s life stage. However, like humans, genetic and environmental factors determine when a dog’s fur turns gray more so than age. Your gray-haired dog could still be quite young, but their fur changed early due to genetics or a rough start in life.
The 6 stages of a dog's life
Dogs experience life stages similar to humans, but they progress at different rates. For example, puppyhood lasts less than a year compared to human childhood, which lasts around 10 to 12 years before puberty. Aging is correlated to breed, as small breeds tend to develop faster and reach seniority slower than large-breed dogs.
1. Puppy
Although people still consider a dog a “puppy” until it’s around 2 years old, it’s only a puppy developmentally until 6 months. During their first half-year of life, your dog will grow exponentially, gaining and losing all of their baby teeth and achieving most of their height during this timespan.
2. Junior
Your dog reaches their challenging adolescent period between 6 months and a year old. Although they may still act like a puppy, they’re rapidly undergoing sexual development and will typically reach reproductive maturity between 9 months and a year.
3. Adult
After their first birthday, your dog will officially be considered an adult. At this time, you can ask your vet about switching them to adult food if you haven’t already, and when to spay or neuter. With most of their linear growth behind them, your dog may continue to fill out and gain weight during their second year of life, losing the gangly appearance they might have had as puppies.
The last three life stages aren’t as straightforward as the first three because they depend on your dog’s breed.
4. Mature
A dog is mature or middle-aged when its metabolism begins to slow. At this point, make sure that they don’t become obese. You might want to talk to your vet about switching to a low-calorie food.
5. Senior
Your dog is considered a senior during the last estimated 25% of their lifespan. For example, a dog that lives about 12 years would be a senior when it turns 9. You might consider switching to a senior diet if you haven’t already since dogs don’t need as many calories or fat as they did in their younger years.
6. Geriatric
Not all dogs live long enough to be considered geriatric, the final period of life where age expectancy is exceeded. As they rapidly slow down, they might develop cognitive problems such as dog dementia, so you’ll need to account for limited mobility, making sure they don’t jump down from furniture and carrying them when traveling a long distance. Still encourage them to exercise, but know their limits and don’t force them.
Frequently asked questions
Is it true that dogs age seven years for every one human year?
Not necessarily. While the previous seven-year calculation might give you a rough estimate, it’s now believed that a new formula is more accurate, one that scientists are still trying to hone. They are working to mathematically account for differences in dog breeds since size and genetics play a huge role in life expectancy.
How do ‘dog years’ work?
Dog years give a general estimate of how old your pup is in human years. However, dogs age differently than humans, and all breeds don’t age at the same rate. In general, dogs age rapidly in their first two years of life, and then their aging process slows down.
How old is a dog at 15?
According to the formula 16ln(dog_age) + 31, a 15-year-old dog is approximately 75 years old. However, that would mean the average Great Dane has a maximum life expectancy of only 67 years. The math isn’t entirely accurate because it doesn’t account for a dog’s breed, which also plays a role in life expectancy, but it’s the closest method we have.
