A simple formula for measuring dog years is to consider each year as equivalent to seven years of human life. This would make a dog seven at the age of one, in human years, and fourteen at the age of two. There is some dispute regarding how to calculate dog years, and most vets agree this formula is very inaccurate for cats. Cat years need to be measured by other standards, especially since some cats can live to be about twenty years of age.
One way of measuring cat years is to look at the maturity of the cat in its first year of life. Many cats reach sexual maturity at the age of six months and are able to reproduce at this time. Some people consider cats to be fifteen years old when they are six months, and about twenty-four years old at the end of their first year of life. There may be some argument regarding this too, and others suggest that a cat reaches the age of fifteen at one year old, then ages the equivalent of nine years the next and would be twenty-four in human years at the age of two.
When you look at charts regarding cat years, there does appear consensus that the aging process slows down once a cat is fully mature. If cat lifespan is compared to human life span, then cat years after the age of one or two are roughly equivalent to four human years per one year of a cat’s life. Depending on which calculation you use, this would make a twenty year old cat about ninety-six or a hundred years old.
You can see why this may be a more accurate measurement than the seven-year plan applied to dogs. Presently, no humans have lived to be one hundred forty, but under the seven-year plan, plenty of cats would reach this age. The common way of calculating dog years really wouldn’t work for measuring cat years, given the advanced age of some cats.
It may be more important to calculate the actual lifespan of your cat, rather than measuring it in cat years. Sadly some cats won’t reach old age because of choices owners make. Unaltered cats tend to have shorter lives and are more at risk for certain kinds of cancer. Cats that live exclusively indoors usually live longer, an average of fifteen years.
The unsupervised cat that lives mostly outdoors may have an average lifespan of about three years, according to the United States Humane Society. Cats with indoor/outdoor privileges may still have long lives, but this really depends upon the safety of the area in which they live and the degree of owner involvement. Sadly many cats don’t make it past the first year or two or are euthanized as kittens due to failure to spay or neuter pets at appropriate times, before they reach sexual maturity.