##
Accelerated Reader Points Formula *July 9, 2007*

*Posted by Jeff in Books.*

trackback

trackback

I found this overview of the Accelerated Reader program, which includes the formula for calculating the number of points a book is worth. The formula is:

AR points = (10 + reading level) X (words in book/100,000).

I tried this formula out on a few different books from Amazon that include the “reading level” and “words in book” numbers. Some point values calculated this way were way off of the numbers posted on the Marietta, Georgia, Accelerated Reader site, but most were close enough to seem useful. The difference may be attributed to any of the following:

- The formula above may be incorrect or may have changed.
- The Amazon and AR methods of calculating the reading level and the number of words in a book may produce different results.
- The Marietta website data could be out of date.

By the way, Amazon.com has a cool (if old) feature for some of it’s books. You may have seen books that allow you to “Search Inside this Book”. For these books, you can also get the text statistics for things like figuring out the Accelerated Reader points. For example: Go to the page for Adventures of Huckleberry Finn and move your mouse over the image of the book. You will see an image like this (forgive the n-word…that’s from Amazon’s text analysis of the book, not from me):

Click on the link that says “text stats” to go to a page that has lots of info about the text of the book itself. For example, it tells us that there are 109,808 words in the book and that the Flesch-Kincaid reading level (index) is 7.3. Using those two numbers in the AR formula above, we can calculate the number of “points” to be 19. By comparison, the Marietta, Georgia, website says that this book is worth 18 points.

Most likely Amazon does not scan the entire book to get the word count. Typically those companies only calculate an average estimate. Renaissance Learning scans the entire book for the AR word count, and it has a proprietary formula for the reading level, so the results should be different when using the other numbers.

Here’s a good source:

http://research.renlearn.com/research/39.asp