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Lexile measures help you find just-right books to match your students’ reading abilities.

But there’s more to a book than a quantitative text complexity metric. To help you engage students even further, many books also get Lexile codes. These codes provide more information about the type of book and its age appropriateness.

The code is a two-letter designation before the Lexile measure. For example, some children’s books seem simple, but are better when adults read them out loud to children. A book like this might get a two-letter designation — AD, or adult directed — which appears before the Lexile measure. A book labeled “AD580L” means that the book is adult directed and is appropriate for students reading at or near a Lexile measure of 580L.

Spanish titles with Lexile measures are divided into similar categories and have Spanish Lexile codes.

For each of these codes, more information and examples can be found below.

The Lexile codes are:

  • AD: Adult Directed: Better when read aloud to a student rather than having the student read independently.
  • NC: Non-Conforming: Good for high-ability readers who still need age-appropriate content.
  • HL: High-Low: Content to engage older students who need materials that are less complex and at a lower reading level.
  • IG: Illustrated Guide: Nonfiction materials often used for reference.
  • GN: Graphic Novel: Graphic novels or comic books.
  • BR: Beginning Reader: Appropriate for emerging readers with a Lexile reader measure below 0L.
  • NP: Non-Prose: Poems, plays, songs, recipes and text with non-standard or absent punctuation.


Picture books are often labeled AD, or “adult directed,” because they are usually read to a child, rather than a child reading them independently. Picture a parent reading a book to a child on the sofa, or a teacher reading a book aloud to the class. Although these books seem like easy reading, some picture books can still present a challenging independent reading experience to an age-appropriate reader for reasons of text difficulty, book layout or design.

Take the example of Maurice Sendak’s Where the Wild Things Are (HarperCollins Publishers), a beloved read-aloud book for preschoolers. However, it has a Lexile text measure of 740L, which is around the average reading ability for a child completing fourth grade. When you look closely at the text, you can see why it gets a “higher” Lexile text measure than the intended audience. The sentences are long and contain fairly high-level vocabulary such as “mischief,” “private,” “gnash” and “rumpus.” The parent or educator would help the preschooler sound these words out and decipher these long sentences. Therefore, the book is coded AD (adult directed) and the measure is AD740L.

Additionally, picture books can have design elements that may visually complicate reading for a child. Factors such as font size, typeface, page layout, legibility and the relationship between pictures and text may significantly impact reading comprehension. The story and illustrations in Where the Wild Things Are are perfect for young children. But the lines of the text are close together and the sentences are spread over multiple pages, often in long horizontal lines. These design elements may challenge a child’s ability to read the book independently even if the text difficulty is well matched. Initially, a more advanced reader may need to read the book with a child.

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NC: Non-Conforming

Sometimes, high-ability readers have trouble finding books that challenge their reading skills but still have age-appropriate content. The NC code helps identify these books, which have received a higher Lexile text measure but are appropriate for a younger audience.

For example, Seymour Simon’s Amazing Aircraft (SeaStar Books) is coded NC900L. Its spine reads “grades 1-3” but its Lexile measure is higher than a typical early elementary school student’s ability range. This book might be hard to read for most students in grades 1-3, but engaging and challenging for students with above-average reading abilities. Therefore, the book is coded as NC (non-conforming) and would be appropriate for a student in grades 1-3 with a Lexile reader measure at or near 900L.

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HL: High-Low

A text designated as “HL” has a Lexile text measure much lower than the average reading ability of the intended age range of its readers. Librarians and booksellers sometimes refer to young adult books with disproportionately low Lexile measures as “high-low” books, meaning “high-interest” plus “low-readability.” These books receive an HL code. Fiction HL books are often useful when matching older (grade seven and beyond) struggling or reluctant readers with text at both an appropriate difficulty level and an appropriate developmental level.

Despite their short sentences and basic vocabulary, HL books are designed to appeal to readers at a more mature developmental level. For example, Beth Goobie’s Sticks and Stones (Orca Soundings) is classified as a young adult book and measures 430L — the average Lexile reader measure for second graders. The book’s characters are high-school students who struggle with the many challenges that face high-school students such as dating and gossip. Therefore, the book is coded HL430L.

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IG: Illustrated Guide

The IG code is applied to books that consist of independent pieces or sections of text such as in an encyclopedia or glossary. These text pieces could be moved around without affecting the overall linear flow of the book. Nonfiction IG books are often used as a reference resource rather than read in their entirety like a storybook. Their distinguishing text characteristics include:

  • technical vocabulary, definitions and pronunciation guides in parentheses or contrasting type
  • integration of illustrations and diagrams into the text
  • pull-quotes, factoids and other categorical marginalia
  • the presentation of each discrete topic on one to two pages

These text characteristics do not necessarily impact reading comprehension or developmental appropriateness. Instead, the IG code conveys an idea of the kind of book and what the book typically will be used for in the classroom or library.

Birds of Prey by Dr. Gerald Legg (Franklin Watts Library) is coded IG. Separate paragraphs are arranged upon the page, functioning more like multiple-sentence captions. A particular reading order is neither indicated by the layout nor important to comprehension. Thus the book measure is IG980L.

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GN: Graphic Novel

The GN code indicates that the book is a graphic novel or comic book. The text of GN books appears primarily in voice or thought bubbles integrated into comic book-style illustrations. Graphic novels tend to contain a larger percentage of dialogue than most other genres of books. They also typically lack some of the required text conventions of dialogue, such as putting “she said” after a quoted sentence, because illustrations are used to indicate spoken text. The impact of picture support on reading comprehension is not captured in the Lexile measure of a graphic novel. To Dance: A Ballerina’s Graphic Novel (Aladdin), written by Siena Cherson Siegel and illustrated by Mark Siegel, is coded as GN610L.

Also see this article from Edutopia about the instructional value of using graphic novels and comics in the classroom.

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BR: Beginning Reader

Beginning Reader (BR) is a code given to readers and text that are below 0L on the Lexile scale. In some cases, for readers, a BR code is followed by a number and L (e.g., BR150L). A Lexile reader measure of BR150L indicates that the Lexile measure of the reader is 150 units below 0L. The lower the number following the BR code, the more advanced the reader or text is. The higher the number, the less complex the text is or less skilled the reader is.

Note that Beginning Reader (BR) is the only Lexile code that applies to both readers and text. All other codes apply only to text. Learn more about the Beginning Reader code and the recent enhancements to more precisely match beginning readers to text.

Good Night, Gorilla by Peggy Rathmann (Random House) is a BR book with a Lexile measure of BR50L.

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NP: Non-Prose

Some books don’t receive Lexile text codes because they are aren’t prose. These books might feature poems, plays, songs, recipes and text with non-standard or absent punctuation. The NP code is for any book comprising more than 50% non-standard or non-conforming prose. NP books do not receive a Lexile measure, merely the NP code.

An example of a book coded NP is Maurice Sendak’s Alligators All Around (HarperTrophy). The text of the book is not in complete sentences and lacks punctuation entirely. The text difficulty of such a book cannot currently be assigned a Lexile measure.

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Have more questions about finding the appropriate book for your students?

Visit the Lexile® Find a Book  tool or our Lexile Support Center.