Teachers, parents, students and publishers use the Lexile Framework for Reading to determine a reader's ability to comprehend written text. Most standardized assessments administered in school calculate the student's current Lexile measurement. Scores range from about 200 Lexile (200L) for beginning readers to 1,700L or greater for advanced readers who can comprehend complicated and difficult reading material. A student's Lexile level depends on reading ability, not age or grade level.

The Lexile Framework for Reading uses the same scale to determine a student's reading level and the difficulty level of books, magazines, websites and other reading materials. Teachers, parents and students use Lexile levels to choose reading materials a particular student can comprehend without frustration. As of 2009, more than 150 publishers provide Lexile measurements for their books and publications.

A book's Lexile level measures how difficult its text is to understand. The Lexile Framework measures two factors: semantic difficulty, also known as word frequency, or how often the same words appear in a passage of text, and syntactic complexity, or the average sentence length in a passage of text. Books with long sentences and few repeated words are more difficult to comprehend and receive a higher Lexile measurement. Books with short sentences and many repeated words are easier to comprehend and receive a lower Lexile measurement.

Determining a Book's Lexile Level

To determine the Lexile level of a book, the text is divided into 125-word sections. Word frequency and sentence length are calculated for each section. The results are compared with the Lexile scale, and the book is given a corresponding Lexile level.

The Lexile scale allows students and parents to tailor reading materials to each student's current reading ability and choose books both challenging and understandable. The results of almost all major standardized tests taken in K-12 schools in the United States show a student's current Lexile level. Matching the reader's Lexile level to a book of approximately the same level means the reader should be able to comprehend about 70 percent of the book's text. A reader whose Lexile measurement is 400L, for example, should be able to comprehend about 70 percent of any book within 50L of his measurement (350L to 450L). Educators believe that the 70 percent comprehension level is ideal for students because they can read without feeling frustrated, while still learning new vocabulary and improving their reading skills.


The Lexile level of a book indicates only how easy or difficult it is to comprehend. The Lexile framework does not measure whether the book's content is age-appropriate. Students with a high Lexile score for their age may be able to comprehend more challenging reading material, but the content of that material may not be appropriate for their age. Parents and teachers should examine the content of reading material in addition to its Lexile measurement.