Found this when I did google search.

Use the chart below to determine your cat's age in relation to a human's.

Cat's Age: .............................Human's Age:

6 months.......................................10 years
8 months.......................................13 years
10 months......................................14 years
1 year..........................................15 years
18 months......................................20 years
2 years.........................................24 years
4 years.........................................32 years
6 years.........................................40 years
8 years.........................................48 years
10 years........................................56 years
12 years........................................64 years
14 years........................................72 years
16 years........................................80 years
18 years........................................88 years
20 years........................................96 years
21 years.......................................100 years