Contrary to popular wisdom, a year in the life of a feline is not the same as seven years for their human caretaker. Instead, a one-year-old cat is equivalent to a 16-year-old human adolescent. A two-year-old cat is equivalent to a 21-year-old person. After that, each cat year is equivalent to four human years.
Therefore, a 5-year-old cat would be 33 years old in people years. A 10-year-old cat would be 53, and a 15-year-old kitty would be 73 in human years.