Pet Age Calculator
How old is your pet in human years? Worked out by species and size, with the life stage they have reached and what to change in their care.
Why isn’t one dog year equal to seven human years?
Multiplying by 7 is the old rule of thumb. A dog's first year already takes them to around 15 in human terms, the second adds another 9, and only then does it slow down - and large breeds age faster than small ones. So the AKC and AVMA now use a table where dogs age more quickly during their first two years and each year after that adds 4 to 7 depending on size; for cats it is 15 and 24 for the first two years, then 4 a year. This calculator follows those two tables, interpolating by month.
Dog age chart (AKC, by size)
| Dog age | Small | Medium | Large | Giant |
|---|
Cat age chart
| Cat age | Human years | Stage |
|---|
What counts as senior, and what changes?
The definition vets use is the last quarter of the expected lifespan: from about 10 for small dogs, 8 for medium, 7 for large and 6 for giant; cats count as senior from 11, with 7 to 10 being mature. The change is not overnight - from that stage you start watching the joints, cognition, heart and urinary health, and move from the adult line to the Senior Advanced line. Dogs over 7 can go straight to Senior Dogs; if they are not there yet, 30-second buying guide will pick by age for you.
Frequently asked questions
Why do large dogs age faster?
The general view in the research is that large dogs grow fast and carry more metabolic stress at the cellular level, so the conditions associated with ageing (joints, heart) show up earlier - which is why the same dog age maps to more human years for large and giant breeds.
Which size do I use for a mixed breed?
Use the adult weight: under 10 kg is small, 10 to 25 kg medium, 25 to 45 kg large, over 45 kg giant. Mixed breeds usually live a little longer than pedigrees of the same size.
How much difference does indoor versus outdoor make for cats?
Indoor cats generally live 13 to 17 years; cats that go outside or are semi-free-roaming live noticeably shorter lives because of accidents, infections and fights. The lifespan progress here uses the indoor median of 15 years.
Chart sources: the American Kennel Club's How to Calculate Dog Years to Human Years, the AAHA 2019 canine life stage guidelines, and the AAHA / AAFP 2021 feline life stage guidelines. Lifespans are median figures by size, for reference rather than prediction; if there are symptoms, see your vet.
