Many of us wonder how old our dog is in human years, sometimes using it as a gauge to decide how our dog must feel compared to our own aging bodies. The old standby is that one year of a dog’s life equals seven years in a human’s life. It’s easy to do mathematically, and it does give you a ballpark idea, but it’s no longer considered accurate, especially for younger dogs.
According to a 2020 study from the University of California at San Diego, the seven-year equation needed to be refined. Very simply put, the researchers used DNA changes to determine that a 1-year-old dog would be equivalent to about a 15-year-old person. This fits with puberty coming about that age for many dogs.
At the age of 2, the study showed dogs are comparable to around a 24- or 25-year-old human, a change of about nine human years.
After that, the USCD plan shifts to about five human years for each dog year.
However, there remains a discrepancy with toy breeds, who often hit 17 or 18 years of life, and giant breeds who are often elderly at 7 years or so. So, while this new method of calculating dog years into human years is based on scientific research, it doesn’t (yet!) compensate for the breed or size differentials in lifespans.
The Supporting Research
The USCD study included 104 Labrador Retrievers spanning a 16-year age range. The researchers scanned the dogs’ DNA patterns for comparison and used the rate of the methylation changes in the dogs to match it to the human epigenetic clock (biological aging). They then proposed a new formula of comparing dog years to human years for dogs over the age of 1. Much of the research on aging (in any species) looks at how DNA ages, particularly methylation, as this study did. The genes controlling this change in DNA appeared to be similar for both the Labrador Retrievers in the study and humans.
The study is fascinating, and you can access it as a beautifully illustrated report with charts of the study. The study conclusions were accepted by the American Veterinary Medical Association and most veterinary professionals support the findings.
The Dog Aging Formula
The study’s math is a complicated formula, requiring you to be able to calculate your dog’s age in natural logarithm (not how many years he’s been alive), multiplied by 16, plus 31. Using this formula, a 6-year-old dog would be equivalent to a human who is 59.7 years old, instead of the old method that would compare the dog to a 42-year-old human.
While most of us aren’t going to do the math, other examples of how this works out include a 7-week-old puppy being similar to a 9-month-old baby (with both of them teething at that age), and the average Labrador (who lives to about 12 years of age) correlating to a 70-year-old human (the Centers for Disease Control and Prevention say the average lifespan for humans is 76).
Health Matters to Dog Aging
An undisputed fact in lifespan calculations is that for all dogs – and humans, too, for that matter – keeping your dog fit, trim, and active, while practicing appropriate preventive health care and feeding good nutrition, is the best way to give your dog a long, full life. Of course, genetics do matter, so it helps to get a dog whose pedigree includes dogs who lived long lives, if you can obtain that information.