The traditional way of aging pets:

CAT OR DOG AGE	HUMAN EQUIVALENT
1 year	7 years
2 years	14 years
3 years	21 years
4 years	28 years
5 years	35 years
6 years	42 years
7 years	49 years
8 years	56 years
9 years	63 years
10 years	70 years
11 years	77 years
12 years	84 years
13 years	91 years
14 years	98 years
15 years	105 years
16 years	112 years
17 years	119 years
18 years	126 years