Tracie Hotchner, author of The Cat Bible, offers a slightly different variation on the aforementioned calculation. In this alternative formula, Hotchner delves more specifically into the corresponding ages of young kittens to similarly young human children. Here, courtesy of Hotchner, is the answer to the question, “How old do cats live in human years?”

• 1-month-old kitten = 6-month-old human baby
• 3-month-old kitten = 4-year-old child
• 6-month-old kitten = 10 human years old
• 8-month-old kitten = 15-year-old human
• A 1-year-old cat has reached adulthood, the equivalent of 18 human years
• 2 human years = 24 cat years
• 4 human years = 35 cat years
• 6 human years = 42 cat years
• 8 human years = 50 cat years
• 10 human years = 60 cat years
• 12 human years = 70 cat years
• 14 human years = 80 cat years
• 16 human years = 84 cat years