DogYearsThe dog age formula, explained
In 2020, researchers found a way to compare dog and human ageing directly in DNA — and the result was a logarithm, not the number 7.
Worked example — a 3-year-old dog: ln(3) ≈ 1.0986 → ×16 ≈ 17.6 → +31 = ≈ 48.6 human years.
The idea: methylation clocks. As mammals age, chemical marks called methyl groups attach to DNA in patterns regular enough to act as a clock. Tina Wang, Trey Ideker and colleagues at UC San Diego measured those patterns in dogs and humans and aligned the two clocks. Where the marks matched up, they could read off how old a dog is “in human methylation years” — and the relationship that fell out was logarithmic.
Why a logarithm makes sense. A logarithm grows quickly at first and then flattens — which is exactly how dogs develop. The jump from puppy to adult happens in months; the difference between a 9- and a 10-year-old dog is far smaller. A straight multiple like 7 cannot bend, so it fails at both ends of life.
The limits, stated plainly. The study fitted the formula on 104 Labrador Retrievers — one large breed, from one population. It therefore knows nothing about size, and nothing directly about Chihuahuas, greyhounds or mixed breeds. It is also a methylation comparison, not a measure of health, fertility or cognition. We include it because it is genuine, widely reported science, and because its disagreements with the veterinary chart are themselves informative.
Where it applies. From roughly 0.15 years upward. For very young puppies the curve is not meaningful, so the homepage calculator flags that instead of printing a number.
Questions
What is the dog age formula from the DNA study?
Human age = 16 × ln(dog age) + 31, where ln is the natural logarithm. It was published in 2020 by a UC San Diego team led by Trey Ideker, with Tina Wang as first author, based on DNA methylation patterns measured in 104 Labrador Retrievers aged from a few weeks to 16 years.
How do I calculate 16 × ln(age) + 31 by hand?
Take your dog's age in years, find its natural logarithm (the ln button on a scientific calculator), multiply by 16, and add 31. For a 3-year-old: ln(3) ≈ 1.0986, × 16 ≈ 17.6, + 31 ≈ 48.6 human years. The calculator on our homepage does it instantly.
Why does the formula only work for older puppies?
Methylation changes extremely fast in the first weeks of life, and the fitted curve is generally applied from about 0.15 years (roughly 8 weeks) upward. Below that, the logarithm produces meaningless numbers, so our calculator says so rather than inventing a figure.
Is the DNA formula more accurate than the vet chart?
They measure different things. The formula describes how methylation ageing in Labradors maps onto human methylation ageing; the chart is a clinical rule of thumb refined over decades of practice, and it can express size. Neither is a ground truth for an individual dog — we show both, labelled, so you can see the range.