Calculating the age of your pet in cat years is not the same as the formula you use for dogs. Cats do not age in the same manner as dogs or humans.
Cat Lifespans
Cat lifespans start with quick aging in the first year of their life, but then they slow down.
If they followed the pattern of a dog, a 20-year cat would be the equivalent of 140 years old, and veterinary experts agree this could not be possible. As a result, the correct way to calculate your pet's cat age changes after the first year.
Geriatric cats age similarly to humans, though still a bit faster. However, they still aren't similar to a dog's aging process, which is seven years for every one human year.
Cat Age Equivalent Calculation
When your cat is six months old, he is the equivalent of a 15 year old. By the age of one, he's gained another nine years and is now 24.
After your cat reaches the age of one, the pattern slows down. The cat ages four years for the additional cat years. At age two, your cat is 28, at three, 32, and at four, 36. Therefore, when your cat turns 10, he is 60 years old.