Levels: Book, Interest, and Reading

Book level, interest level, and reading level measure different things.

Book Level

Book level represents the difficulty or readability of the text. The available book levels are:

ATOS book levels are assigned using the ATOS readability formula and range from 0.1 (least difficult) to 20.0 (most difficult).

For example, a book level of 4.5 means that the text could likely be read independently by a student whose reading skills are at the level of a typical fourth-grade student during the fifth month of school.

The content may or may not be appropriate for a fourth-grade student, which is why interest levels are also used.

To search for books by book level range, see steps 6 and 7 in the Advanced Search option.

A Lexile® measure represents the complexity of a text, such as a book or article. Lexile measures are expressed as numeric measures followed by an "L" (for example, 850L), and are placed on the Lexile scale. The Lexile scale is a developmental scale for measuring reader ability and text complexity, ranging from below 200L for beginning readers and beginning-reader materials to above 1600L for advanced readers and materials.

Values displayed as Lexile® measures that are not followed by an "L" are estimates of Lexile text measures based on a study conducted by MetaMetrics® using ATOS Book Levels and are not certified Lexile measures. The Lexile code gives you more information about a book that relates to its developmental appropriateness, reading difficulty, and common or intended usage. Visit for more information.

Your school may or may not use the Lexile scale; ask your child's teacher.

you must first perform an Advanced Search.

  1. In the search criteria, choose an interest level.
  2. To show both the ATOS book level and the Lexile measure in search results lists and on book details pages, select Show Lexile® measure.

Interest Level

The interest level relates to the content and age appropriateness of a book or article.

Books and other reading materials are assigned an interest level based on publisher recommendations. The interest level reflects the judgment of the book's publisher and the professionals at Renaissance. However, the final decision on whether the content of a book is appropriate for a particular student is the responsibility of school librarians, teachers, and parents.

Within each interest level, you will find a wide range of book levels to support students who read at, above, or below grade level.

Accelerated Reader Bookfinder uses these interest levels:

  • LG (Lower Grades, K–3)
  • MG (Middle Grades, 4–8)
  • MG+ (Middle Grades Plus, 6 and up)
  • UG (Upper Grades, 9–12)

Reading Level

Reading level is a student's tested reading level ranging from 0.0 (lowest) to 13.0 (highest).

Reading level indicates the most difficult text a student can comprehend based on a standardized test (such as Star Reading) or results from Accelerated Reader Reading Practice quizzes. Your child's reading level helps to determine the range of book levels your child should select books from. For example, if your child's reading level is 1.4, your child's teacher may suggest the child pick books with book levels between 1.4 and 2.4.

Your child's teacher may provide your child's reading level to you. The reading level may be presented as:

Grade Equivalent scores range from 0.0 (lowest) to 13.0 (highest).

Your child's GE score is presented as a specific number (example: 3.3).

GE scores represent how a student's test performance compares with that of other students nationally.

The ZPD ranges from 0.0 (lowest) to 13.0 (highest).

Your child's ZPD is presented as a range (example: 3.2–4.9).

The Zone of Proximal Development suggests the book-level range from which a student should be selecting books for optimal growth in reading without frustration.

The ZPD is especially useful for students using Accelerated Reader.

The ZPD, however, is approximate. Success at any reading level also depends on the student's interest and prior knowledge of a book's content.

Teachers should use their professional judgment to adjust the level of books read to match an individual student's needs and interests.