If your cat is five years old, that means he is the same physiologic age as a 35-year-old person, right? Well, actually not. The theory that every year in a cat's life is the same as seven years in ours is commonly known but unfortunately not very accurate.
For example, a one-year-old cat has passed puberty. A seven-year-old child likely has not. The average life span of a cat is 14 years. The average person does not live to be 98 years old.
For a more accurate comparison between physiologic age of cats, follow this formula:
A one-year-old cat is about 15 human years old. When the cat reaches two, he is the equivalent of a 24-year-old person. After that, each year is about 4 human years. This means that a nine-year-old cat is about the same as a 52-year-old person.
Another factor that plays into the life span of a cat is whether or not he lives outdoors or indoors. A 16-year-old indoor neutered or spayed cat is the equivalent physiologically as an eight-year-old outdoor unneutered/unspayed cat.
By the time most cats reach seven years of age, they are entering their senior years. The record for the longest feline life span is 36 years.