A 11-year-old West Highland White Terrier in human years

West Highland White 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 class15–20 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

Breed: West Highland White Terrier
Age: 11 years

Two answers, and neither is simply wrong

60 human years by the AVMA size-based table: 15 for the first year, 9 for the second, then 4 a year for a small breed.

69 human years by the epigenetic clock published in Cell Systems in 2020 — human age = 16 × ln(dog age) + 31, derived from DNA methylation.

They differ by 9 years here. The epigenetic clock is a measurement rather than a convention and captures early life remarkably well, but it was calibrated on Labradors and cannot see breed size. The AVMA table does account for size but is a smoothed consensus.

Bigger dogs age faster

This is backwards from mammals in general, and it is why no single conversion 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.

Where this dog is

Life stage: mature. Roughly 73% through a typical lifespan for a small breed, with a median of 15 years.

Those are population medians from veterinary data, not a forecast — individual dogs of every size routinely live well past them.

The one thing that moves the number

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 your control.

Notes

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.

Nearby sizes

French Bulldog Harnesses: Why the Chart Almost Always Reads SmallThe French Bulldog is the breed weight-based charts get most wrong, because almost none of its measurements are where the weight suggests they should be.
Measuring a Dog for a Harness: Three Numbers, Ninety SecondsGirth sizes the harness. Neck decides whether it goes on. Almost every returned harness is one of four measuring errors rather than a bad chart.
No-Pull Harness Sizing: Why Fit Decides Whether It Works at AllA front-clip harness is the one style where fit is not a comfort question. Half an inch of slack and the mechanism it depends on simply stops happening.
Puppy Harness Sizing: Why Age Is the Worst Index of AllAge tells you less about a puppy's chest than any other variable, because two puppies of the same age can be six months apart in development and four sizes apart in girth.