Pet age in human years
The "multiply by seven" rule is wrong, and it is most wrong for the pets people worry about. Dogs age fastest in their first two years, then slow — and a Great Dane ages far quicker than a Chihuahua.
How cats age
Cats age far more consistently than dogs, because adult size varies much less between breeds. A Maine Coon and a domestic shorthair follow broadly the same curve, which makes feline age conversion more reliable than the canine equivalent.
The first two years
A cat reaches roughly fifteen human-year equivalents by its first birthday and about twenty-four by its second. Growth, sexual maturity and full adult behaviour are all complete inside two years. After that the pace steadies at roughly four human years per calendar year.
Indoor and outdoor
The single largest influence on feline lifespan is not breed or diet — it is whether the cat goes outside. Traffic, territorial fights, infectious disease and predation all shorten outdoor life expectancy substantially. Indoor cats commonly reach their late teens.
When to change care
Cats are classed mature from around seven and senior from about eleven. This matters more than it does in dogs, because cats conceal illness effectively. Twice-yearly examinations and baseline bloodwork from the mature stage catch kidney and thyroid disease long before an owner would notice anything wrong.
Weight loss in an older cat is never normal ageing. It is one of the earliest signs of hyperthyroidism, kidney disease and diabetes, and it is worth a same-week appointment rather than a wait-and-see.
Common questions
Is the cat and dog conversion the same?
No. Cats age more uniformly because adult size varies little between breeds, whereas dog ageing depends heavily on adult weight.
How long do indoor cats live?
Commonly into their late teens, with some reaching twenty or beyond. Outdoor access reduces average lifespan considerably.
When is a cat senior?
Mature from around seven and senior from about eleven. Veterinary guidance recommends more frequent checks from the mature stage rather than waiting for senior.
My old cat is losing weight but eating well. Is that normal ageing?
No. Eating well while losing weight is a classic sign of hyperthyroidism or diabetes and should be investigated promptly.