A patent-protected electronic leveling system determines the Lexile level of books by considering factors including sentence length, word frequency and syntanic and symantic challenges present in the text. The resulting numerical Lexile level represents the overall complexity of the text a as a whole.
While the specific formula used to determine the Lexile level is a trade secret, certain characteristics of a text can reliably be tied to producing a higher or lower Lexile level determination. In terms of sentence length, texts with longer sentences are assigned a higher Lexile score than those with shorter sentences, as shorter sentences allow for easier comprehension of the text. Texts with more frequent repetition of words are deemed easier for the reader and, as a result, books with high word frequency are assigned a lower Lexile score.
The analysis of syntatic and symantic references is vastly more complicated. In general, books with more traditional syntax, or word order, are labeled as easier than texts with more complex sentences. Similarly, texts with less figurative language earn a lower Lexile score. While the analysis process is a closely guarded secret, parents, teachers and students can determine the Lexile levels of books using the "Find a Book" feature available on the official website.