Dog Age in Human Years

Dog age converted two ways — the AVMA size-based table and the 2020 epigenetic clock — with the life stage and share of a typical lifespan that the number is really standing in for.

Multiply by seven and you will be wrong in both directions — badly wrong for a one-year-old, badly wrong again for a fifteen-year-old.

A dog reaches sexual maturity in its first year. No seven-year-old human has. And a fifteen-year-old small-breed dog is old but not 105.

Two better answers, and they disagree usefully

The AVMA size-based table. Fifteen human years for the first year, nine for the second, then four to six and a half a year depending on size. It is a smoothed professional consensus and it accounts for the thing that matters most — body size.

The epigenetic clock, published in Cell Systems in 2020: human age = 16 × ln(dog age) + 31. It comes from DNA methylation patterns rather than convention, and it fits early life remarkably well — it puts a one-year-old at 31, which matches the biology better than any table.

Its limitation is that it was calibrated on Labradors and cannot see breed size at all.

Bigger dogs age faster, and that is backwards

Across mammals generally, larger species live longer. Within dogs the relationship inverts: a great dane's median lifespan is around half a chihuahua's. Nobody has a complete explanation, and it is why no single conversion works for every breed.

The number that is actually useful

Not the human-years figure — the life stage, and how far through a typical lifespan the dog is. That is what changes what you do: twice-yearly vet visits instead of annual ones, bloodwork, joint support, and watching for the things that are cheap to manage early and expensive to manage late.

The one lever that moves it

Weight. A landmark Purina lifetime study found dogs kept lean lived about 1.8 years longer than littermates fed 25% more. That is a larger effect than almost anything else within an owner's control.

Breed

Age (years)

A 11-year-old Wire Fox Terrier in human years

Wire Fox Terrier at 11 years

60human years

small breed — mature, roughly 73% through a typical lifespan

AVMA size-based15 for year one, 9 for year two, then 4/year for a small breed	60human years
Epigenetic clock16 × ln(age) + 31 — Wang et al. 2020, calibrated on Labradors	69human years
Difference between the twothey disagree — see the note below	+9years
Life stage	mature
Size class15–18 lb — larger dogs age faster	small
Typical lifespanmedian for small breeds	15years
Share of life so far	73%
Typical years remaininga population median, not a prediction about your dog	4years

Notes

Wire Fox Terrier. 13 to 15 years. Lens luxation is a genuine emergency in this breed and appears between three and six years.
Bigger dogs age faster, which is backwards from mammals in general and is the reason no single conversion table works. A small breed adds about 4 human years per dog year after the second birthday; a small breed adds 4, a giant breed 6.5. The old "multiply by seven" rule gets a one-year-old badly wrong in one direction and a fifteen-year-old badly wrong in the other.
The two methods differ by 9 years at this age, and neither is simply wrong. The epigenetic clock is measured from DNA methylation and captures early life very well, but it was calibrated on Labradors and cannot see breed size. The AVMA table does account for size but is a smoothed consensus rather than a measurement.
Weight is the single largest thing under your control. A landmark Purina lifetime study found dogs kept lean lived about 1.8 years longer than littermates fed 25% more, which is a bigger effect than almost anything else you can do.
Lifespan figures are population medians from veterinary data, not a forecast. Individual dogs of every size routinely live well past them.

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Dog age in human years

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