Gunning Fog Index

Gunning Fog Index

(the easiest to use and probably the most popular readability index)

Steps in Applying the Index

Select a sample
Determine the average number of words per sentence
Determine the percentage of hard words
Add the 2 factors and multiply by 0.4

The result is the minimum grade level at which the writing is easily read!

Sample

In general, construction of pictograms follows the general procedure used in constructing bar charts. But two special rules should be followed. First, all of the picture units used must be of equal size. The comparisons must be made wholly on the basis of the number of illustrations used and never by varying the areas of the individual pictures used. The reason for this rule is obvious. The human eye is grossly inadequate in comparing areas of geometric designs. Second, the pictures or symbols used must appropriately depict the quantity to be illustrated. A comparison of the navies of the world, for example, might make use of miniature ship drawings. Cotton production might be shown by bales of cotton. Obviously, the drawings used must be immediately interpreted by the reader.

Computation

129 words in 10 sentences = asl of 13

26 hard words out of 129 = 20%

Average sentence length Percentage of hard words	13.0 20.0
Total Multiply by	33.0 0.4
Grade level of readership	13.2

Other Popular Indexes

Flesch Reading Ease Score

Rates text on a 100-point scale; the higher the score, the easier it is to understand the document.
Most standard documents aim for a score of 60 to 70.

Flesch-Kincaid Grade Level Score

Rates text on a U.S. grade-school level (same yardstick that the Gunning Fog index uses).

Appraisal of Indexes

Popular because they

reduce to simple formulas the complex work of writing
provide a convenient check and measure of the level of oneís writing
possess the glitter of mathematical exactness
can be calculated by word processing software

Appraisal of Indexes

Limitations

a low style of writing can result from a slavish use of readability indexesóa monotonous succession of short sentences and simple words can make your writing dull and dull writing doesnít hold the readerís attention
the indexes frequently give conflicting results

Best Use of Indexes

Use the formulas as a general guide
Formulas will not replace the clear and logical thinking that is the foundation of all clear writing