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ClickHelp Documentation

Gunning Fog Index

The Gunning Fog Index is a readability metric which uses word and sentence length to determine how difficult a text is to read. Index values typically vary from 0 to 20. Values correspond to the number of years of education a reader requires in order to understand a text. For example, a value of 6 corresponds to 11-12-year-old readers while 12 corresponds to 17-18-year-olds. Values should be interpreted as follows:

Value School level Student age range Notes
0-1 Pre-kindergarten - 1st grade 3-7 Basic level for those who just learn to read books.
1-5 1st grade - 5th grade 7-11 Very easy to read.
5-8 5th grade - 8th grade 11-14 A text is considered ideal for average readers.
8-11 8th grade - 11th grade 14-17 Fairly difficult to read.
11-20 11th grade - college 17 and above Too hard to read for the majority of readers.


Information

Originally, all the metrics were created for the English language and the education system of the United States. In ClickHelp, the metrics are available for all languages. Because of this, school levels and age ranges may be off for other languages. But the relative values will still be correct, so you can compare the readability of two different topics that use the same language. For example, if your topic got 100 according to Flesch Reading Ease, and another topic got 80, it means that the text of the second topic is more difficult to read, than the text of the first one. 


If the value of a readability metric is zero for your topic, check the selected language for your project to make sure it matches the language of the actual text. Also, make sure the punctuation is correct and all sentences end with a dot.