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A 10-year-old Rhodesian Ridgeback in human years

Rhodesian Ridgeback at 10 years
68human years
large breed — senior, roughly 91% through a typical lifespan
AVMA size-based15 for year one, 9 for year two, then 5.5/year for a large breed68human years
Epigenetic clock16 × ln(age) + 31 — Wang et al. 2020, calibrated on Labradors68human years
Difference between the twothe two methods agree closely at this age-0years
Life stagesenior
Size class70–85 lb — larger dogs age fasterlarge
Typical lifespanmedian for large breeds11years
Share of life so far91%
Typical years remaininga population median, not a prediction about your dog1years
Breed
Rhodesian Ridgeback
Age
10 years

Two answers, and neither is simply wrong

68 human years by the AVMA size-based table: 15 for the first year, 9 for the second, then 5.5 a year for a large breed.

68 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 0 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 large breed adds about 5.5 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: senior. Roughly 91% through a typical lifespan for a large breed, with a median of 11 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 large breed adds about 5.5 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 land within 0 years of each other here, which is about as close as they get.
  • At senior stage, twice-yearly vet visits are the standard recommendation rather than annual ones. Most of what shortens a senior dog's remaining time — dental disease, arthritis, kidney and heart changes — is manageable when found early and expensive when found late.
  • Lifespan figures are population medians from veterinary data, not a forecast. Individual dogs of every size routinely live well past them.

Nearby sizes