Flesch Grade Level Readability Formula improves upon the Flesch Reading Ease Readability Formula. Rudolph Flesch, an author, writing consultant, and the supporter of Plain English Movement, is the co-author of this formula along with John P. Kincaid. That's why it is also called Flesch-Kincaid Grade Level Readability Test. Raised in Austria, Flesch studied law and earned a Ph.D. in English from the Columbia University. Flesch, through his writings and speeches, advocated a return to phonics. In his article, "A New Readability Yardstick," published in the Journal of Applied Psychology in 1948, Flesch proposed the Reading Ease Readability Formula.

In 1976 the US Navy modified the Reading Ease formula to produce a grade-level score by applying the Flesch Grade-Scale formula, or the Kincaid formula. John P. Kincaid was assisted by Robert P Fishburne Jr., Richard L. Rogers, and Brad S. Chissom, in his research.

This formula is known by different names, like Flesch-Kincaid Index, Flesch-Kincaid Grade Level Score, Flesch-Kincaid Scale, Flesch-Kincaid Score, Flesch-Kincaid Readability Score, Flesch-Kincaid Readability Statistics, Flesch-Kincaid Grade Level Index, Flesch-Kincaid Readability Index, Flesch-Kincaid readability equation, and so on.

The US Government Department of Defense uses Flesch-Kincaid Grade Level formula as a standard test; however, this Formula is best suited in the field of education.

How to calculate the Flesch-Kincaid Grade Level Readability Formula:

Step 1: Calculate the average number of words used per sentence.

Step 2: Calculate the average number of syllables per word.

Step 3: Multiply the average number of words by 0.39 and add it to the average number of syllables per word multiplied by 11.8.

Step 4: Subtract 15.59 from the result.

The specific mathematical formula is:

FKRA = (0.39 x ASL) + (11.8 x ASW) - 15.59

Where,

FKRA = Flesch-Kincaid Reading Age

ASL = Average Sentence Length (i.e., the number of words divided by the number of sentences)

ASW = Average number of Syllable per Word (i.e., the number of syllables divided by the number of words)

Analyzing the results is a simple exercise. A score of 5.0 indicates a grade-school level; a score of 9.3 means that a ninth grader would be able to read the document. This score makes it easier for teachers, parents, librarians, and others to judge the readability level of various books and texts for students.

Theoretically, the lowest grade level score could be -3.4. This is an unlikely result since no real passages have every sentence consisting of a one-syllable word.

Flesch-Kincaid Grade Level Readability Formula is available in MS-Word. However, MS-Word doesn't score above grade 12; any grade above 12 will be reported as Grade 12.

If your text scores above 12th grade, then follow these simple writing tips to reduce the complexity of your writing:

1. Write below the 8th-grade level. Studies show that writing below the 8th-grade (preferably around 5-6th grade levels) achieves the best results.

2. Get to the point immediately. Don't write long-winded paragraphs that bury your document’s message.

3. Use active voice, not passive. Writing in active voice enables you to write shorter sentences, and write with authority.

4. Always use fewer words when possible.

5. Use simpler words. If you can replace a difficult word with a simpler word, then use the simpler word.