Lexile Framework

A commercial readability framework developed by MetaMetrics that places both texts and readers on a common scale — the Lexile measure — to support matching readers with materials at an appropriate level of challenge. A text's Lexile measure is computed from sentence length and word frequency against a large reference corpus; a reader's measure is obtained from standardised reading tests. Lexile is widely used in U.S. K-12 education for matching students to books, and by publishers and library systems to label content difficulty. For accessibility work, Lexile provides a common vocabulary for discussing text difficulty across audiences but shares the core limitation of surface-feature readability formulas — it does not capture discourse coherence, entity density, or cognitive load.