Cat years to human years and the four life stages

The four life stages (2021)

The 2021 task force defined four age-based stages plus one more:

So an 11-year-old cat is a senior. The American Veterinary Medical Association (AVMA) says the same in plain terms: cats are generally considered senior after 10 years of age. Our calculator counts completed years, so a cat moves into the senior stage on its 11th birthday. A cat of 10 years and 11 months is still counted as a mature adult; by the chart below it is about 60 in human years, the same as its first day as an 11-year-old senior. The line between stages is a convention for planning care, not a change that happens overnight.

The 2021 guidelines cut the number of stages from six to four, plus end of life. The task force says the biology behind six stages still holds, but five groupings make clinical care easier to organize. The point of the stages is to focus attention on the physical and behavioral changes, and the medical needs, that come with each part of life.

Cat years in human years: the 2010 chart

The human-age chart in the 2010 AAFP-AAHA guidelines runs fast through kittenhood: a 1-month-old kitten is equivalent to a baby of up to a year, a 6-month-old to a 10-year-old child, and a 1-year-old cat to a 15-year-old. A 2-year-old cat equals 24. After that, each cat year adds 4 human years.

Between the chart’s rows, our calculator draws a straight line and says so. A 5-month-old kitten comes out at about 9, between the 4-month and 6-month rows.

The 2010 guidelines grouped cats into six stages: kitten (to 6 months), junior (7 months to 2 years), prime (3–6 years), mature (7–10), senior (11–14) and geriatric (15 and up). The 2021 stages replaced them.

Where the chart comes from, and a common mis-citation

The 2010 guidelines describe their stages as a convenient classification developed by the Feline Advisory Bureau, the charity now called International Cat Care. International Cat Care states the same rule in words: the first two years of a cat’s life equal 24 human years, and every year after that equals 4.

Two cautions follow. First, the chart is a convention, a way to talk about age, not a measurement of how fast cats’ bodies change. Second, the 2021 guidelines define stages only; they contain no human-age chart. A calculator that cites the 2021 guidelines for its human years is citing the wrong document.

The chart also shows why multiplying by seven fails for cats as it does for dogs. Times seven makes an 11-year-old cat 77 and a 14-year-old 98; the chart says 60 and 72. Seven is too low for kittens, since a 1-year-old cat is already 15 on the chart, and too high for older cats, because after age 2 the chart adds 4 a year, not 7.

How long cats live

International Cat Care puts the average at around 12 to 14 years and says it isn’t unusual for cats to reach their late teens or early twenties. That is a charity’s summary, not a single study, so read it as a broad guide. By the 2010 chart, a 14-year-old cat is about 72, and a 20-year-old about 96.

What changes for a senior cat

The stage matters more than the human-age number, because it changes the care plan. The 2021 feline guidelines recommend a check-up at least once a year for every cat, and at least every 6 months for seniors, more often for cats with long-term conditions. The AVMA gives the same advice for senior pets: twice a year or more, so problems are found early.

The 2021 guidelines also point out that signs of illness and pain are often hard to spot in cats, which tend to be stoic. They ask vets to teach owners which behavior changes are not just old age, and to record weight, body condition and muscle condition at every visit so slow changes show up as a trend. The AVMA adds that in senior cats weight loss is the bigger worry, while in senior dogs it is weight gain.

Food needs can change in the opposite direction from what people expect. AAHA’s 2021 nutrition guidelines remind vets that cats may actually need more calories later in life. If your older cat is losing weight, that is a reason to see your vet, not to wait. For the calorie side, see how much to feed a cat.

This is general information, not veterinary advice — talk to your vet about what your cat’s stage means for its check-ups and diet.

Next step

Enter your cat’s age or birth date in the cat age calculator for the 2021 stage and the 2010 human-age equivalent. For dogs, where size changes everything, see dog years to human years.