Catage is a very good site where you give in various information such as if your cat is an indoor cat, if you're a smoker and what food you feed your cat in order to calculate it's age. I'll do another test now since the last one I did was over a year ago and I'll post the results here.
Yoda's CatAge is 38.2!
That's 16.1 years younger than the average CatAge for Yoda's breed.

Chewy's CatAge is 41.4!
That's 12.2 years younger than the average CatAge for Chewy's breed.

Gizmo's CatAge is 26.5!
That's 12.4 years younger than the average CatAge for Gizmo's breed.

(CatAge is the biological age of your cat, measured in people years.)