Pet age calculator

Lifespan varies across pets by more than two orders of magnitude, which is what makes a single "pet years" conversion meaningless. Hamsters live two to three years, rabbits eight to twelve, cats and dogs ten to eighteen depending on size, and larger parrots can outlive their owners: a macaw commonly reaches fifty and sometimes eighty. Any life-stage judgement has to start from the species and not from the number.

Within dogs and cats a conversion is worth having, and it is not times seven. The first year is worth roughly fifteen human years, the second about nine, and only then does the rate settle: about four a year for a cat or a small dog, up to seven and a half for a giant breed. Size is the dominant variable in dogs, and it works the opposite way to the usual pattern across species. Larger animals generally live longer, an elephant outlasting a mouse by decades, and yet a Great Dane’s usual span is eight to ten years while a small terrier commonly passes fifteen. Rapid growth and higher rates of age-related disease in large breeds are the leading explanations, and the question is not settled. There is no comparable size effect in domestic cats. The epigenetic figure shown beside the dog conversion is a 2020 formula derived from DNA methylation in Labrador retrievers, 16 × ln(age) + 31; it tracks the underlying biology better than any lookup table and behaves oddly under a year, which is why it sits as a second opinion and not as the headline.

It is worth being exact about whose numbers these are, because "the AVMA chart" is what every dog-age page claims to be printing. The AVMA publishes one dog column, footnoted as a medium dog of 21 to 50 pounds, and it gives 36 at five years, 51 at eight, 60 at ten and 69 at twelve. The model here is size-banded instead — fifteen for the first year, nine for the second, then four a year for a small dog, five for a medium, six for a large and seven and a half for a giant — so its medium band returns 39, 54, 64 and 74 at those same ages, three to five years above the AVMA figure and climbing. The cat column is AVMA’s, verbatim, and so is the small-dog column, which is the identical series: 15, 24, 36, 48, 56, 64. That is exactly what makes the difference easy to miss, so it is stated rather than left to be inferred. Neither approach is a measurement; the AVMA’s own footnote says the ages are approximate and that weight and breed both move them.

None of it helps without a birth date, and rescue animals rarely come with one. What can be read off an animal is species-specific, and it is always the young that can be dated. A kitten’s eyes open at seven to ten days and its permanent teeth are complete by about six months; past that the usable signs are tartar and, from eight or so, the grey haze of lenticular sclerosis in the lens, which is a normal hardening and not a cataract. Rabbits are judged mostly on weight, coat and nail growth, and small mammals barely at all. In every case the estimate stops being a number and becomes a band, so settling on one approximate date and keeping it beats re-estimating every year.