Converting between cat years and human years is not as simple as using a factor of 7 (as some people erroneously think with cats, and sometimes cats). The main reason is that cats mature quickly in the first couple of years of life. To convert cat age to an equivalent human age, an accepted method is to add 15 years for the first year of life. Then add 10 years for the second year of life. After that, add 4 years for every cat year. This means that by year two, a cat has matured to about the same as a 25 year old human.