An old cat must receive much different care than that of a kitten to stay healthy. In order to get an idea of how old your cat is in relation to human terms this chart converts cat years into human years. This will give you an idea of your cat's age so that you can care for him/her accordingly.  cat's age conversion chart cat years human years 1 month 5 to 6 months 2 months 9 to 10 months 3 months 2 to 3 years 4 months 5 to 6 years 5 months 8 to 9 years 6 months 10 years 8 months 13 years 1 year 15 years 2 years 24 years 3 years 28 years 4 years 32 years 5 years 36 years 6 years 40 years 7 years 44 years 8 years 48 years 9 years 52 years 10 years 56 years 11 years 60 years 12 years 64 years 13 years 68 years 14 years 72 years 15 years 76 years 16 years 80 years 17 years 84 years 18 years 88 years 19 years 92 years 20 years 96 years 21 years 100 years