There are several conversion tables from cat age to human age. I picked one from them, because it has a clear basis from their researches. That is:
International Cat Care - How to tell your cat’s age in human years
They have studied the growth of cats for many years. And that introduced this conversion table. They divide cats life time into 6 stages. And they corresponded the growth stage with the stage of human growth.
Acording to that, a cat grows to about 10 years old in six months of calendar age, and 15 y/o in 12 months, 24 y/o in 24 months. After that, it grows 4 y/o in on calendar year. So the table is following;
|Calendar||Age of Cat|
I ploted it in a graph of first 24 months.
Also in 20 years.
This is a table from ICC themselves.
There are 6 life stages for cats:
Kitten – 0-6 monthsa period when the young cat is growing rapidly and is usually not quite sexually matureJunior – 6 months-2 yearsduring this time the cat reaches full size and learns about life and how to survive itPrime – 3-6 yearsthe cat is mature physically and behaviourally, and is still usually healthy and active, looking sleek and shiny and making the best of lifeMature – 7-10 yearsthe cat is what we call 'Mature', equivalent to humans in their mid-40s to mid-50sSenior - 11-14 yearstakes the cat up to the equivalent of about 70 human yearsGeriatric - 15 years and overmany cats do reach this stage, some not showing any signs of being geriatric at all!