Researchers at the University of California San Diego School of Medicine have developed a new formula that takes into account that variance. Tracking molecular changes in the DNA of Labrador retrievers, and in particular “the changing patterns of methyl groups” in their genome, according to a release, the study shows how dogs age at a much faster rate than humans early in their lives, then slow down after reaching maturity.

“This makes sense when you think about it — after all, a nine-month-old dog can have puppies, so we already knew that the 1:7 ratio wasn’t an accurate measure of age,” lead author Trey Ideker is quoted as saying.

Based on the study, a one-year-old dog compares to a 30-year-old human, a four-year-old dog to a 52-year-old human. The rate of aging decreases after dogs turn 7.