Suffolks are large, symmetrical and uniform in color and type. Their frames are supported by clean, dense bone. Due to their extreme draftiness, the legs of the Suffolk appear short and are strongly muscled in forearms and gaskins. They are placed well under the horse and are free of long hair. Their excellent feet are round, of fair size and wear extremely well, shod or unshod.
Suffolks possess intelligent heads with active ears, powerful and arching necks that are clean cut at the throat. The shoulders are inclined to be upright, suitable for power rather than action. The back is short and strong, the ribs springing high from the backbone. The quarters are long and smooth to the root of the tail, which springs higher up than in other breeds. The hipbones are wide apart but smoothly covered, the croup usually level.
Depth and thickness from the withers to the leg are essential and a Suffolk should be as deep in the flank as over the heart.
Characteristically the whole appearance of the Suffolk is a pleasant, roundly modeled whole that pertains, like the singleness of color, to no other breed.
The average height of a Suffolk horse is 16.1 hands, but many stallions may stand up to 17 hands and more.
This information is from the American Suffolk Horse Association website.