Size 2 dresses in U.S. fashion are designed for women with a waist between 23.75 inches and 26 inches. A size 2 converts to "extra small" size in the United States and a size 4 or size 6 in the United Kingdom.
A woman's size 2 is not the smallest size offered by all designers; some designers offer sizes 0, 00 and 000.
A natural waist is measured between the hips and bust, and is generally the point where humans tip from side to side just below the ribs. A tape measure should be kept loose when measuring a waist so clothing does not fit too tightly.