Domestic cats are similar in size to the other members of the genus Felis, typically weighing between 4 and 5 kg (9 and 10 lb).
Some breeds, such as the Maine Coon, can occasionally exceed 11 kg (24 lb). Conversely, very small cats, less than 2 kg (4 lb), have been reported. The world record for the largest cat is 21 kg (50 lb) The smallest adult cat ever officially recorded weighed around 1 kg (2 lb). Feral cats tend to be lighter as they have more limited access to food than house cats. In the Boston area, the average feral adult male will weigh 4 kg (9 lb) and average feral female 3 kg (7 lb). Cats average about 23–25 cm (9–10 in) in height and 46 cm (18 in) in head/body length (males being larger than females), with tails averaging 30 cm (12 in) in length.
Cats have seven cervical vertebrae, as do almost all mammals; 13 thoracic vertebrae (humans have 12); seven lumbar vertebrae (humans have five); three sacral vertebrae like most mammals (humans have five); and a variable number of caudal vertebrae in the tail (humans retain three to five caudal vertebrae, fused into an internal coccyx). The extra lumbar and thoracic vertebrae account for the cat's spinal mobility and flexibility. Attached to the spine are 13 ribs, the shoulder, and the pelvis. Unlike human arms, cat forelimbs are attached to the shoulder by free-floating clavicle bones which allow them to pass their body through any space into which they can fit their head.