A size 30 jean measures 30 inches at the waist. However, size 30 jeans may be offered in different inseam lengths dependent on the manufacturer.
Each denim manufacturer offers different options, and it is important to refer to the designer's fit guide to get physical measurements. A size 30 Levi's jean measures only 27 to 28 inches in the waist, while the 7 for All Mankind size 30 mid-rise skinny jean measures 29 and 1/4 inches at the waist. In addition to fit variations between manufacturers, different fits are available within the same brand as well. For example, the measurements of a size 30 mid-rise skinny jean are not the same as a low-rise boyfriend fit jean.