Donaldson R F Pet Age Calculators
Nine calculators that turn a pet’s age into something you can picture. Each result carries a label that says how far the number can be trusted, and the sensitive species (small rodents, birds, tortoises and turtles) never get a made-up ‘human age’. Nothing you type leaves your browser.
| Pet | What you get | Human-age label | Other results |
|---|---|---|---|
| Dog | Human-equivalent age, AAHA life stage | Scientific formula | Life stage: Veterinary life-stage guideline |
| Cat | Human-equivalent range, AAHA/AAFP life stage, share of a typical lifespan | Popular rule of thumb — rough idea only | Life stage: Veterinary life-stage guideline; Lifespan: Popular rule of thumb — rough idea only |
| Horse | Human-equivalent range, ‘aged’ and ‘very old’ ages, share of a typical lifespan | Popular rule of thumb — rough idea only | Life stage: Peer-reviewed scientific article; Lifespan: Popular rule of thumb — rough idea only |
| Rabbit | Human-equivalent range, RSPCA life stage, share of a typical lifespan | Popular rule of thumb — rough idea only | Life stage: Veterinary life-stage guideline; Lifespan: Veterinary life-stage guideline |
| Guinea pig | Life stage and share of a typical lifespan (no human years) | Not shown | Life stage: Popular rule of thumb — rough idea only; Lifespan: Popular rule of thumb — rough idea only |
| Hamster | Share of a typical lifespan (no human years, no life stages) | Not shown | Lifespan: Veterinary life-stage guideline |
| Budgerigar | Share of a typical lifespan (no human years, no life stages) | Not shown | Lifespan: Popular rule of thumb — rough idea only |
| Cockatiel | Share of a typical lifespan (no human years, no life stages) | Not shown | Lifespan: Popular rule of thumb — rough idea only |
| Tortoise or turtle | Published lifespans by species group (no human years) | Not shown | Lifespan: Veterinary life-stage guideline |
How this works
Quick answer
Only the dog calculator uses a published scientific formula. For cats, horses and rabbits the human-age figure is a popular rule of thumb, so we show it as a range and say so. For guinea pigs, hamsters, budgerigars, cockatiels, tortoises and turtles we show no human years at all, only what welfare and veterinary sources say about life stages and lifespan.
The three confidence labels
- Scientific formula: a formula fitted to research data, read in the original paper. Only the dog calculator has one (Wang and colleagues, 2020, fitted to Labrador retrievers).
- Veterinary life-stage guideline: stages or lifespans published by a veterinary body or an animal-welfare organisation (for example AAHA, AAFP, the RSPCA or the PDSA) whose page we read. These give ages for stages of life, not human equivalents.
- Popular rule of thumb — rough idea only: a rule that appears only in secondary sources such as care websites. We read at least two, show the result as a range (the multiples of five that enclose it), list what we read, and found no primary scientific basis. Treat it as a way to picture your pet’s life, not as a measurement.
Why animal age and human age are not exact equivalents
Species grow, mature and age in different ways, and even within one species breed, size, health and environment matter. A ‘human age’ is a comparison for people, not a medical fact about the animal. Where we found no defensible conversion we say so instead of inventing one.
What is not here
We only built calculators where we could read a source for the numbers. Other species (for example ferrets, chinchillas, parrots other than budgerigars and cockatiels, goats, and lizards or snakes) are not covered, and the tortoise and turtle page covers only the species groups listed on it.
Every calculator page lists its sources with links and the date we checked them (27 September 2026). To work out the gap between two dates for people or pets, use the Age Calculator.