J. Jill utilizes a specialized sizing structure designed to accommodate a diverse range of body types, offering standard misses sizes, petite proportions, tall options, and dedicated women's plus sizes. Their numerical and letter-based sizing system typically spans from extra-small to extra-large (or numeric equivalents from standard single digits up to extended plus measurements), with detailed body measurement guides provided on their official website. These online charts outline exact bust, waist, hip, and inseam dimensions to help customers select the correct fit across their apparel categories.