Pet Age Calculator
A practical age estimate with species and size adjustment
Human-age equivalents are approximate; use life stage and veterinary advice for care decisions
Quick guide
What can Pet Age Calculator help you do?
Free pet age estimator for cats and dogs with size adjustment and life-stage guidance. Human-age equivalents are approximate, not a veterinary standard.
Best for
Use this for an informal comparison between a cat or dog age and the human-equivalent age produced by this model. Dogs have three size options. The life-stage label is a separate age classification, not a health score or lifespan forecast.
How to use it
Choose cat or dog, then select a size for dogs. The starting example is a three-year-old medium dog. Enter whole years from 0 to 30 and additional months from 0 to 11; the display updates automatically and clears for a nonpositive combined age.
How to read the result
For dogs aged at least one year, the model uses 16 times the natural logarithm of age plus 31, with multipliers of 0.92 for small dogs and 1.1 for large dogs. Cats over two use 24 plus four per additional year. Results are rounded.
Privacy and limits
This widget calculates from species, size, years and months in the browser, without submitting those inputs or saving a pet profile. No owner name, microchip number or medical history is needed. Avoid adding identifying details when sharing a screenshot.
Different formulas apply to different age bands, creating jumps at some boundaries, particularly when a dog turns one. These jumps describe the model, not a sudden biological change. The estimate is not a diagnosis, care recommendation or substitute for an individual veterinary assessment.
Frequently Asked Questions
Why isn't dog age just "× 7"?
The "× 7" rule is a 1950s rough estimate. UC San Diego 2020 research showed dog aging is logarithmic, not linear. Formula: human age = 16 × ln(dog age) + 31.
How is cat age calculated?
Cat standard: Year 1 = 15 years, Year 2 = 24 years, then +4 per year.
Do different dog sizes age the same?
No. Large breeds (> 25 kg) age faster, lifespan 8–10 years. Small breeds can live 14–16 years. We adjust for size.
My puppy is 6 months old, how to calculate?
Set "Age" to 0 and "Extra months" to 6. Puppy aging is handled separately (non-linear).
How are life stages categorized?
Puppy/Kitten (< 1 yr), Young Adult (1–3), Adult (3–7), Senior (7–10), Geriatric (> 10). Common veterinary standard.