How dog years are calculated here
The calculator uses the formula from Wang et al., "Quantitative Translation of Dog-to-Human Aging by Conserved Remodeling of the DNA Methylome", Cell Systems, 2020 (free full text). The researchers measured DNA methylation, chemical marks on the DNA that change with age, in the blood of 104 dogs, primarily Labrador retrievers, aged 0.1 to 16 years. They compared each dog with blood samples from 320 people aged 1 to 103 and fitted one function that translates dog age to human age:
Here ln is the natural logarithm and the dog age is in years. A dog of 3 years is 16 × ln 3 + 31 = 48.6 human years. For a 12-year-old Labrador, the breed's expected lifespan in the study, the formula gives about 71 human years, close to the worldwide human life expectancy of 70 that the authors compared it with.
Why not simply times seven?
The study set out to test the adage that one dog year equals seven human years. The DNA methylation data showed a nonlinear relationship instead: the dog methylome changes very rapidly in puppies compared with children, and the change slows markedly in canine adulthood. That is why a 1-year-old dog lands at 31 and a 16-year-old at 75, while the times seven rule says 7 and 112.
Dog years to human years chart
| Dog age | Human years (formula) | Times seven |
|---|---|---|
| 1 year | 31 | 7 |
| 2 years | 42 | 14 |
| 3 years | 49 | 21 |
| 4 years | 53 | 28 |
| 5 years | 57 | 35 |
| 6 years | 60 | 42 |
| 7 years | 62 | 49 |
| 8 years | 64 | 56 |
| 9 years | 66 | 63 |
| 10 years | 68 | 70 |
| 11 years | 69 | 77 |
| 12 years | 71 | 84 |
| 13 years | 72 | 91 |
| 14 years | 73 | 98 |
| 15 years | 74 | 105 |
| 16 years | 75 | 112 |
The chart stops at 16 years, the oldest dogs in the study. The calculator goes up to 25 years, but beyond 16 the formula is used outside the data it was fitted on.
Life stages in dogs and humans
The authors lined up the formula with approximate life stages, based on veterinary guides for dogs and on the human life cycle (Figure 3D of the paper). They found the closest match for the infant, juvenile and senior stages, and a looser one for adolescent and mature dogs.
| Stage | Dogs | Humans |
|---|---|---|
| Juvenile | 2 to 6 months | 1 to 12 years |
| Adolescent | 6 months to 2 years | about 12 to 25 years |
| Mature | 2 to 7 years | 25 to 50 years |
| Senior | after 7, to a life expectancy of 12 years | after 50, to a life expectancy of 70 years |
Limits of the formula
- One breed. The dogs were primarily Labrador retrievers. The authors note that breeds with widely varying lifespans could yield different functions.
- Very young puppies. Below about 2 months, the formula gives values near zero or below, so the calculator starts there.
- Blood only. The methylation was measured in whole blood, and the authors list that as a limitation.
How to use the dog age calculator
- 1Enter your dog's age in years, and months if you know them.
- 2Read the age in human years, rounded, with the exact value and the life stage below.
- 3Copy the result or a link to it. For a cat, use the cat age calculator; for your own exact age, the age calculator.
Frequently asked questions
How old is my dog in human years?
With the formula from the 2020 study by Wang and colleagues, human age = 16 × ln(dog age) + 31, where ln is the natural logarithm. A 3-year-old dog comes out at 16 × ln 3 + 31 = 48.6 human years. Enter your dog's age above and the calculator does this for you.
Is one dog year really seven human years?
Not according to this study. The researchers compared age-related changes in DNA methylation of dogs and humans and found a nonlinear relationship: the dog methylome changes very quickly in puppies compared with children, then slows markedly in adult dogs. So a young dog is "older" than seven times its age, and an old dog "younger".
Does the formula work for small and large breeds?
It was fitted to dogs that were primarily Labrador retrievers. The authors write that breeds with widely varying lifespans could yield different age translation functions, so for very small or very large breeds the result is a rough guide only.
Why does a 1-year-old dog come out at 31?
Because the natural logarithm of 1 is 0, the formula gives 31 human years at a dog age of 1 year. That reflects what the study found: the dog methylome changes very rapidly in puppies compared with children. In the life stage table of the paper, a dog is an adolescent from 6 months to 2 years, a human from about 12 to 25 years.
Can I use it for a young puppy?
The study included dogs from 0.1 years old, but at a very young age the formula gives values near zero or below. The calculator therefore starts at 2 months, where the result is just over 2 human years.
Is my data sent anywhere?
No. The calculation runs in your browser, nothing is stored or sent.