Adult domestic cats normally weigh from 2 to 8 kg, an average of 3.5 kg. All other structural features vary greatly - the shape of the head and muzzle, the length of the legs, body and tail, and the size of the ears. The life expectancy of cats is often exaggerated, but many cases are reliably known when they survived to 20 years. However, the usual life span of a cat is 10-15 years.