The long-believed "1 dog year = 7 human years" theory is not supported by science. Different breeds age differently, with small dogs in general living longer than large ones. A 2019 study suggests a new formula based on changes made to dogs' DNA over time.
So a 7-year-old dog would be roughly 62.1 human years old.
People observed that with optimal healthcare, an average-sized, medium dog would on average live one-seventh as long as its human owner – and so the seven “dog years” for every “human year” equation was born.
The first year of a dog's life is equal to 15 human years. The second year of a dog's life is equal to about nine human years. Each additional year is equal to about four or five human years.
Well, dogs are in possession of faster metabolisms and hearts that work harder than our own. Because of all this extra work, dogs age faster and, consequently, live shorter lives. It also means they grow up more quickly. A dog that's a year old is the equivalent of a human child ready to start school.
The most challenging time of raising a puppy is the adolescent period. Dogs become “teenagers” and seem to forget everything they have ever been taught. This period is individual to each dog, but it may begin when he's about eight months old and continue until he's two years old.
Most dogs enter their senior years at around 7 years old, a little sooner for larger dog breeds. They begin to slow down, they may gain weight more easily, their senses start to dull. An older dog's behavior will give you plenty of hints as to what he needs, but sometimes it helps to put it in words.
CHANG: So they gathered blood samples from 100 Labrador retrievers, from pups to old dogs, and studied the chemical decorations on their DNA. In doing so, the scientists were able to build a clock to compare biological age across species.
According to the formula, a 2-year-old dog is the equivalent of a 42-year-old human, but things slow down after that. A 5-year-old dog is the equivalent of a 56.75 year old human, and a 10-year-old dog is the equivalent of 67.8-year-old person.
Georges Buffon, an 18th-century French naturalist, had more or less the same theory: Humans live to 90 or 100 years, and dogs to 10 or 12.
No one knows where the dog years rule came from, though virtually all dog owners know it. According to that popular myth, every year a dog spends on the planet is equivalent to seven years for a human. So if a dog lives to be 15 years old, she's actually 105 in human years.
Instead, when your dog enters this stage can vary greatly depending on your pooch's breed and size. While many people estimate the average age at which a dog becomes a senior at about 7 years old, this can actually vary considerably between the ages of 5 and 12.
The Senior Stage
It is important to cherish each stage as a dog's golden years will begin roughly between the ages of 7 and 10.
A common rule of thumb for dog owners is that one year for dogs is equivalent to seven human years. But new research shows that young puppies age much faster than young humans do, so that simple one-to-seven year ratio is wrong. A 1-year-old dog is more "like a 30-year-old human," one scientist said.
The average lifespan for dogs is between 10-13 years, though there is variability among breeds and sizes.
15 human years equals the first year of a medium-sized dog's life. Year two for a dog equals about nine years for a human. And after that, each human year would be approximately five years for a dog.
Dogs were considered an important member of the human family, helping people hunt, about 8,000 years ago. Ultimately, that relationship led to the idea of dogs as pets—tamed animals kept for companionship inside the home—which can be seen as early as 2,000 years ago during the Roman years, Larson said.
Small dogs are considered senior citizens of the canine community when they reach 11-12 years of age. Their medium-sized friends become seniors at 10 years of age. Their larger-sized colleagues are seniors at 8 years of age. And, finally, their giant-breed counterparts are seniors at 7 years old.
Small breeds are considered senior dogs around 10-12 years old. Medium size breeds are considered senior dogs around 8-9 years old. Large and giant breeds are considered senior dogs around 6-7 years old.
"We believe the relationship between a dog's body size and their lifespan may be caused by an evolutionary lag in the body's cancer defenses, which are unable to keep up with the rapid and recent selective breeding of bigger dogs," he said.
“The older they get, the more sleep they need, and that's OK,” says Dr. Rossman. Just like senior citizens need more sleep, an older dog sleeps a lot when compared to their younger counterparts. On the higher end of the scale, a senior dog can sleep up to 18-20 hours a day, says Dr.