The Fog Index is a measure of the readability of a sample of text. The number is supposed to be the number of years of formal education you would need in order to easily understand the text on the first reading.
So why does anyone care about something like that? If you’re writing for a specific audience, it can be very useful. Most of your average would-be bestsellers are written around 7 or 8--easily read by people with a wide variety of educational backgrounds. Magazine articles, reports, letters...all will be more effective if the text is easily readable by the target audience. In fact, if you’re writing any non-fiction for a clearly targeted audience, the fog index (or one of the other scales used to quantify readability--the fog index is only the most popular of these) is indispensable. If you’d like to calculate your own fog indexes, the formula can be found here. Or use our handy-dandy, automated fog-indexer.
In fiction in general the usefulness of the fog index is less clear. Different sentence structures and word choices can often be used for effect, not to produce a consistent, straightforward readability level--and that’s how it should be. But in some cases, the fog index of a novel or short story can say something about the author’s expectations of her readers. And certainly the inability to vary fog index in different situations says something about the abilities of an author.
The editorial staff at Bo the Lungfish became interested in fog indexes while trying to quantify differences in writing styles--not that they really answered any of our questions, but they became a piece of trivia we found intriguing. So we present them for your amusement, as well.
