The St. Bernard is a giant dog. The average weight of the breed is between 65 and 120 kg (140 and 260 lb) or more, and the approximate height at the withers is 70 to 90 cm (28 to 35 in). The coat can be either smooth or rough; the smooth coat being close and flat while the rough is dense, flat, and more profuse around the neck and legs. The color is typically a red shade with white or a mahogany brindle with white. Black shading is usually found on the face and ears. The tail is long and heavy, hanging low. Eyes are usually brown, but sometimes can be icy blue, and should have naturally tight lids, with haws only slightly visible.
Known as a classic example of a Gentle Giant, the Saint Bernard is calm, patient, and sweet with adults, and especially children. However St. Bernards, like all very large dogs, must be well socialized with people and other dogs in order to prevent fearfulness and any possible aggression or territoriality. The biggest threat to small children is being knocked over by this breed's larger size. Overall they are a sweet, gentle, calm, loyal, and affectionate breed, and if socialized are very friendly. Because of its large adult size, it is essential that proper training and socialization begin while the St. Bernard is still a puppy, so as to avoid the difficulties that normally accompany training large dogs. An unruly St. Bernard may present problems for even a strong adult, so control needs to be asserted from the beginning of the dog's training. While generally not instinctively protective, a St. Bernard may bark at strangers, and their size makes them good deterrents against possible intruders.