Pet Age Calculator
A comparison hub: enter one age to see how dogs of each size and cats are staged and compared, side by side. For your own pet, use the species page — it asks for details this hub doesn't.
Before you start
Method : one age compared across dog size bands and cats, using the Dog and Cat pages' models.
Checked : table values tested at 5 and 8 years; sources checked 5 October 2026.
Review : not reviewed by a veterinarian.
Your entries stay in this browser tab; nothing is sent or stored.
Enter an age to compare.
Species pages
- Dog — weight-based size, AAHA stage, two human-years methods
- Cat — AAHA/AAFP stage, rule-of-thumb chart
- Rabbit — review pending
- Guinea pig — review pending
- Hamster — review pending
- Bird — review pending
- Horse — review pending
- Fish — review pending
- Turtle / tortoise — shell size vs published sizes; no age from size
- Snake — review pending
- Lizard — review pending
How to Use This Calculator
- Enter a birth date or an age
- Press Compare
- Open your species' page for a fuller result
Methodology & assumptions
Uses exactly the same models as the Dog and Cat pages: dog size chart 15 / +9 / then 4, 4.5, 5, 6, 7 per year (toy → giant; AKC/AVMA breakdown plus site size convention), AAHA 2019 dog stages with senior at 75% of a broad size lifespan midpoint; cat chart 15 / 24 / +4 and 2021 AAHA/AAFP stages. Ages from completed calendar months (no 365-day division).
Worked examples
5 years: toy 36, small 38, medium 39, large 42, giant 45, cat 36 human-years — a 9-year spread between dog sizes alone.
8 years: giant dog = senior; medium dog = mature adult; cat = mature adult.
Understanding your result
Human-years are playful analogies, not veterinary science. Life stages are care categories. Neither predicts lifespan for an individual pet.
Sources & further reading
Frequently Asked Questions
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