At what age is a dog senior?

It depends on size: large breeds are often considered senior at five to six years and small dogs around seven (AKC). VCA frames it as roughly the last quarter of expected lifespan.

At what age is a cat senior?

International Cat Care lists senior as 11 to 14 years and super senior as 15 and over; VCA considers cats senior from about 10.

How accurate is this calculator?

It applies published guidelines exactly, but any guideline is an average. Breed, size, weight and health change how an individual pet ages. Use it to know when to adjust care, not as a medical fact.

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Pet age calculator: dog and cat years to human years

Enter your pet's age and get the human-year equivalent using the guideline veterinary bodies publish, not the old seven-to-one rule. The result also tells you which life stage your pet is in and when care should change.

By the PetVitale editorial team · Last reviewed 2026-10-19

Pet

Adult size

Age in years

Plus months

Roughly equivalent to

29 human years

Adult (senior from about 7 for a medium dog)

Guideline: about 15 human years for the first year, 9 for the second, then about 5 per year (AVMA guideline, via AKC). Larger dogs age faster and are considered senior earlier.

How this tool works

Choose dog or cat; for dogs, choose the adult size, which sets when the dog is considered senior.
Enter the age in years and months.
Read the human-year equivalent and the life stage, then see the matching care guide.

The method behind the number

Dogs: the American Kennel Club, citing the American Veterinary Medical Association, gives about 15 human years for a dog's first year, about 9 for the second, and about 5 for each year after that for a medium-sized dog. Larger breeds age faster and are often considered senior at five to six, small dogs around seven. The AKC calls the seven-to-one rule outdated.

Cats: International Cat Care gives 15 human years at age one, 24 at two, and 4 per year after that, with life stages kitten (0 to 6 months), junior (7 months to 2 years), adult (3 to 6), mature (7 to 10), senior (11 to 14) and super senior (15 and over).

Both scales are population guidelines. A DNA-methylation formula published in 2019 (human age ≈ 16 ln(dog age) + 31) gives different numbers and was derived from 104 Labrador Retrievers, so we use the simpler veterinary guideline here.

Questions about this tool

Sources

How to calculate dog years to human years — American Kennel Club (citing the AVMA), updated September 14, 2026
How to tell your cat's age in human years — International Cat Care, updated November 28, 2025
Senior dog care — VCA Animal Hospitals

Senior dog care guide Senior cat care guide Dog health guide Cat health guide

This tool is general information, not veterinary advice. It runs in your browser; what you type stays on your device unless you choose to save it to a PetVitale account. Always confirm schedules, doses and decisions with your veterinarian.