Free tool
Pet age calculator
Seven species, published veterinary guidelines, and an honest account of where the models disagree. It takes about ten seconds and nothing you enter is stored.
Built from the AAHA canine and AAHA/AAFP feline life stage guidelines, the AAEP senior horse recommendation and published lifespan data. Every source is listed below.
Your result will appear here
Choose an animal and enter an age. Nothing you type is sent anywhere or stored.
Species we deliberately left out
- Birds
- Lifespan varies by orders of magnitude across commonly kept species. A budgerigar and a macaw are not comparable, and no cross-species model survives that spread.
- Reptiles
- Ageing rate and lifespan vary enormously by species and by husbandry, and many groups show very little age-related decline.
- Fish
- Lifespan is dominated by species and water quality rather than by age-related decline, so no general model applies.
Evidence and method
Method
How this works
The whole model, in plain language. Nothing here is hidden behind a black box.
- Life stage comes first, because it is the useful answer
- For dogs, cats and horses the stages are taken straight from published veterinary guidelines. For the small mammals, no equivalent guideline exists, so we derive the stages proportionally from a sourced typical lifespan and label them as proportional rather than dressing a proportion up as a guideline.
- The dog senior threshold moves with size, because the guideline says it should
- The AAHA guidelines define senior as the last quarter of estimated lifespan. A giant breed and a small breed have very different estimated lifespans, so they reach that point years apart. We compute it per size band rather than picking one age for every dog.
- Where two models disagree, we show both
- For dogs the staged veterinary convention and the 2020 epigenetic clock genuinely disagree, and not by a little: at one year old they give about 15 and about 31 human years. We show the span between them and name both, rather than picking a winner and implying a precision neither has. Below one year the logarithmic model is undefined, so we simply do not apply it there.
- Very young animals get a stage but no human-age number
- An eight week old puppy is not meaningfully any number of human years. Early growth and human development do not line up, so below a species-specific threshold we suppress the comparison and explain why. The life stage still answers the question.
- We ask for size, not breed
- The published models consume adult body size, not breed. Asking for a breed the calculation never reads would be a way of looking clever rather than being useful.
Limits
What this cannot tell you
- Every result is an estimate, not a measurement.
- This tool does not predict how long your pet will live.
- This tool does not assess health. Breed, genetics, body condition, environment, chronic illness and veterinary care all change the picture.
- Human-age comparisons are a way of explaining a life stage, not a biological equivalence. There is no single agreed conversion for any species.
- If you have a health concern about your pet, speak to a veterinarian.
Sources
Where this comes from
Every source we used, what it supports and when we retrieved it. If one of these changes, this page is wrong and we want to know.
American Animal Hospital Association
2019 AAHA Canine Life Stage Guidelines
The four dog life stages, and the rule that senior begins at the last quarter of estimated lifespan, which is why our senior threshold moves with adult size instead of sitting at one fixed age.
Retrieved 29 July 2026
American Animal Hospital Association and American Association of Feline Practitioners
2021 AAHA/AAFP Feline Life Stage Guidelines
The four cat life stages: kitten to 1 year, young adult 1 to 6, mature adult 7 to 10, senior over 10.
Retrieved 29 July 2026
American Veterinary Medical Association
AAHA updates Canine Life Stage Guidelines
That dogs age at a size-dependent rate in adulthood, which is what the staged conversion's 4 to 6 human years per adult year reflects.
Retrieved 29 July 2026
National Institute on Aging (NIH)
Epigenetics study updates the dog-human age formula
The epigenetic clock from Wang et al. 2020, human age = 16 x ln(dog age) + 31, and its limitation of being derived largely from a single breed.
Retrieved 29 July 2026
American Association of Equine Practitioners
Helping Your Horse Through Its Golden Years
The horse senior threshold of about 15 years, taken from the recommendation that horses over 15 receive wellness examinations at least annually.
Retrieved 29 July 2026
Merck Veterinary Manual
Overview of Rodents, Rabbits and Ferrets
The typical lifespan ranges for rabbits, guinea pigs, hamsters and ferrets that the proportional life-stage model is derived from.
Retrieved 29 July 2026
Questions
Common questions
Is the seven times rule accurate?
No, and no veterinary source uses it. Dogs mature very fast in their first two years and then age at a rate that depends on adult body size, so a single multiplier is wrong at both ends. This tool uses the staged veterinary convention and the 2020 epigenetic model instead, and shows you where they disagree.
Why do you show a range for dogs but a single figure for cats?
Because the evidence differs. For dogs there are two well-established published models that give materially different answers, so showing one number would hide a real disagreement. For cats the sources we reviewed agree, so a range would imply an uncertainty that is not there.
Why can I not choose a bird, reptile or fish?
Because no credible general ageing model exists for them. Lifespan across commonly kept birds varies by more than an order of magnitude, many reptiles show very little age-related decline, and fish lifespan is dominated by species and water quality. A number here would be invented, so we do not offer one.
Does this tell me how long my pet will live?
No. It shows a typical lifespan range for the species, which is a population figure, not a prediction about your animal. Nothing here can forecast an individual lifespan and nothing here assesses health.
Is anything I type saved?
No. The calculation runs entirely in your browser, nothing is sent to a server, and there is no account. If you copy a link to your result, the values travel in that link and nowhere else.
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