Dog Years Calculator
Convert your dog's age into human years — using the modern science-based approach, not the old "multiply by 7" myth. Dogs age fast early then slow down, and size matters, so this adjusts for your dog's build.
How to use this calculator
- Enter your dog's age in years.
- Pick its size — small dogs age slower late in life, giants faster.
- See the human-equivalent age and life stage.
Formula used
This comes from a 2019 study comparing DNA methylation (an "epigenetic clock") in dogs and humans. It captures how dogs mature very fast early — a 1-year-old dog is developmentally a teenager — then age more slowly, which the flat ×7 rule completely misses.
Example calculation
A 5-year-old medium dog: 16 × ln(5) + 31 = ~57 human years — a mature adult.
The ×7 myth would say 35, badly underestimating a dog's true maturity at this age. A 1-year-old dog is already ~31 in human terms.
Why the ×7 rule is wrong
The familiar "one dog year equals seven human years" is a myth with no scientific basis — it seems to have arisen simply as a rough way to say dogs age faster. Real dog ageing is nonlinear: dogs reach the equivalent of human adolescence within their first year and are fully mature adults by two, then age more gradually. A 2019 study using epigenetic clocks (chemical changes to DNA that track biological age across species) produced a logarithmic formula that fits this curve far better.
Size adds a second dimension the old rule ignores entirely. Small breeds tend to live longer and age more slowly in later life, while giant breeds age faster and have shorter lifespans — a Great Dane is genuinely "older" than a Chihuahua of the same age. This calculator applies the science-based formula and adjusts for build, giving a much truer picture of your dog's life stage, which matters for knowing when to watch for age-related health changes.
Why use this calculator?
- Uses the 2019 science-based formula, not the debunked ×7 rule.
- Adjusts for size — giants and small breeds age differently.
- Shows the life stage, useful for age-appropriate care.
Frequently asked questions
How old is my dog in human years?
Use the science-based formula: about 16 × ln(age) + 31. A 2-year-old dog is roughly 42 in human terms, a 5-year-old about 57, adjusted for size. The old ×7 rule is inaccurate — dogs age fast early then slow down.
Is the multiply-by-7 rule accurate?
No — it has no scientific basis and badly misrepresents how dogs age. Dogs mature to adulthood within about two years (far faster than ×7 implies for the early years), then age more gradually. The logarithmic formula fits reality much better.
Does dog size affect ageing?
Yes. Small breeds generally live longer and age more slowly in later life; giant breeds age faster and have shorter lifespans. So a large dog is biologically 'older' than a small dog of the same calendar age. The calculator adjusts for this.