For years the general rule of thumb to equate a cat's age to her human pet was seven human years for each cat year. However, more is known about how cats grow and develop so that old wives tale has been dismissed. In reality, a cat grows in leaps and bounds her first year, slowing down considerably after her first birthday.
A Running Start
Anyone who's experienced the joy of a kitten in the house knows how quickly a little cat turns into a full-grown cat. By the time your kitten is 6 months old, she's able to present you with a litter of her own kittens. Her bones are fully grown around the time she celebrates her first birthday. If you chart your cat's first year against your own growth, she'll be approximately 24 in human years by the time she blows out her first candle. After that first year, her growth levels out and she ages approximately four human years for every one of her cat years. At 3 years old, she'll equal about 32 years; at 6 years, 44 human years; and by 10 years old, she'll be approaching senior citizen status, at 60 human years.