Pets New Zealand
Cat Age Calculator New Zealand
Cats pack a lot of growing into their first two years and then age more slowly. This calculator uses the commonly cited veterinary guide, 15 human years at one, 24 at two and four more for each year after, to give a human-equivalent age and the life stage your cat is in.
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Human-equivalent age
—Life stage
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Cat age in months
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Typical lifespan
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Vet checks suggested
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The working
A guide, not a vet's opinion. General information, not veterinary advice. Every cat ages differently, so speak to your vet about your cat's health and care.
How old is my cat in human years?
A cat is about 15 in human years at one, 24 at two, and gains four human years for every cat year after that. A 10-year-old cat is about 56 in human years. Cats of 10 are in the mature to senior range, so twice-yearly vet checks are sensible.
Life stages
Kittens grow fast and need vaccinations, worming, desexing advice and socialisation. Juniors and prime adults need play, a balanced diet and yearly checks. Mature and senior cats, from about seven years, benefit from checks for kidneys, teeth, thyroid and arthritis, because cats hide illness well. Geriatric cats, over about 15, need extra comfort and care.
Care by age
Change food as your cat's needs change, keep it at a healthy weight and give it somewhere warm and easy to reach. Look for changes in drinking, weight, litter habits or grooming, which can be early signs of illness. Microchipping is not compulsory for cats in New Zealand, but it is strongly recommended, and registration is voluntary.
To compare with your dog, use the dog age calculator.
How this is calculated
The rule, step by step, so you can check any figure by hand.
1 year = 15 human years; 2 years = 24 human yearseach year after the second adds 4 human yearsunder one year, the 15 human years are spread over the 12 monthslife stages: kitten to 6 months, junior to 2 years, prime 3 to 6, mature 7 to 10, senior 11 to 14, geriatric 15 and overindoor cats typically live longer than cats that roam outdoors
The 15-24-then-four pattern is a convention used by veterinary bodies and cat-health groups. It matches the way cats mature quickly early and then age gradually, and it lines up with the life stages vets use. It is not an exact measure, and individual cats vary with genetics, diet, dental health and lifestyle.
Indoor cats commonly live into their mid to late teens, while cats that roam outdoors face more risks from cars, fights and disease, and often live a few years fewer. A cat's weight, teeth and kidney health matter more to its wellbeing than its birthday.
A worked example
A cat aged 10 years.
- Human-equivalent ageabout 56
- Life stageMature, nearing senior
- Typical indoor lifespanabout 15 years
- Vet checkstwice a year
About 56 in human years.
Weight and teeth are worth checking at every visit.
Indoor and outdoor cats
Cats kept indoors are protected from traffic and many infections, and indoor cats tend to live longer. Outdoor cats may also hunt native wildlife, which is a concern in both countries. Keeping cats in at night is a simple way to protect birds and your cat.
What it leaves out
Breed, health and lifestyle differences are not modelled. The result is a guide to think about your cat's stage of life.
What this calculator does not do
- Veterinary convention, not a measurement
- Averages across cats
- Under-one-year ages are approximate
- Not veterinary advice
Common questions
How old is a 10-year-old cat in human years?
About 56.
When is a cat a senior?
From about 11 years.
Do indoor cats live longer?
Typically yes.
How often should an older cat see the vet?
Twice a year is common advice.
Is a cat year really seven human years?
No. The first two years are much bigger.
Where these numbers come from
- New Zealand Veterinary Association New Zealand's veterinary body, for pet health and life-stage guidance
Method last reviewed 2026-10-28 This calculator uses fixed rules rather than rates that change, and its method is re-checked against the sources above at least once a year. Out of date? Tell us and we will fix it.
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