Okay so I found a close accurate age chart in years:

Human years/Cat years

1/15
2/24
3/28
4/32
5/36
6/40
7/44
8/48
9/52
10/56
11/60
12/64
13/68
14/72
15/76
16/80
17/84
18/88
19/92
20/96
21/100
22/104
23/108
24/112
25/116

Remember, moons are months so take however old your cat is in human years and multiply it by 12 to get how many moons your cat is