To Ensure Readability, Use the Fog Index

Every tutorial on writing I’ve reviewed stresses the importance of readability. But clearly that message still has not registered with many editors. Fortunately there are several formulas at hand for achieving tighter writing. My favorite always has been the Fog Index.

I learned about the Fog Index on my first publishing job, as an assistant editor. Our company’s editorial director required all new staff to read The Technique of Clear Writing by Robert Gunning. The book explains how to find levels of reading difficulty using a measure Gunning called the Fog Index. His system helped writers produce prose at a grade level that readers could easily grasp. (Sadly, Gunning’s book is no longer in print. Used copies, however, can be found on Amazon.)

The Fog Index is not like questionable “management by adjectives” approaches to writing skill measurement. In that approach, constructive criticism takes the form of advice such as “too long” or “needs trimming” or other vague directives. By contrast, the Fog Index provides a clear, quantitative approach to readability. Its premise is that an effective writing level falls between 10th and 12th grade reading levels.

Finding Fog Index grade level

You can find the Fog Index grade level by taking a passage of roughly 100 words and performing the following calculations:

1. Determine average sentence length.
2. Count the number of “hard words” (that is, words of three or more syllables, excluding proper names). Divide by the total number of words and multiply by 100 to find the hard word percentage.
3. Add the numbers for average sentence length and hard-word percentage. Multiply the result by 0.4.
4. Drop any decimals from the resulting number. This produces the passage’s grade level.

As an example, let’s analyze the second paragraph of this discussion (the one beginning with “I learned about”):

1. It is 66 words long with four sentences.
2. It includes 7 hard words for a hard-word percentage of 9 (7 divided by 66).
3. Adding the average sentence length (16) and the hard-word percentage (9.4) results in 25.4. Multiplying 25.4 by 0.4 results in 10.2.
4. Drop the decimal point to arrive at a grade level of 10.

Now apply your defogging skills to the following paragraph.

Original Version

The FDA Food Safety Modernization Act (FSMA) is transforming the nation’s food safety system by shifting the focus from responding to foodborne illness to preventing it. Congress enacted FSMA in response to dramatic changes in the global food system and in our understanding of foodborne illness and its consequences, including the realization that preventable foodborne illness is both a significant public health problem and a threat to the economic well-being of the food system.

FDA has finalized seven major rules to implement FSMA, recognizing that ensuring the safety of the food supply is a shared responsibility among many different points in the global supply chain for both human and animal food.

This 112-word sample includes 14 hard words (16%) and three sentences (average sentence length = 37 words). Adding 16 and 37 and multiplying the total of 53 by 0.4 results in a Fog Index of 20, far above the readability goal of 10 to 12.

Defogged Version

The FDA Food Safety Modernization Act (FSMA) is transforming the nation’s food safety system. Rather than simply reacting to foodborne illness, this act aims to prevent it.

Congress passed the act in response to profound changes in the global food system and in our understanding of foodborne illness and its consequences. Lawmakers understood that foodborne illness threatens both the public health and the economic health of the food system.

To implement the act, FDA has finalized seven major rules. These rules assume that the safety of the food supply is a shared responsibility. They therefore address many different points in the global supply chain for both human and animal food.

In this simplified version, we have 110 total words and 7 sentences, producing an average sentence length of 16 words. There are 10 hard words, or 9%. Adding 16 and 10 together and multiplying the total of 26 by 0.4 results in a Fog Index grade level of 10.

Readability Pitfalls to Avoid

Systems like the Fog Index should make readable writing commonplace. But on the Web—and in magazines too—long-winded writing lives on. Parades of endless sentences are the rule rather than the exception. And here’s a puzzling thing: In some cases where a magazine’s content is fast-paced, website copy written by the same staff is plodding.

Why does this happen? Any seasoned editor reviewing submitted copy should see right away that 40-word sentence sequences need deflating. Even chief editors can fall victim to foggy prose. While judging an industry publishing competition’s best editorial column category, I found several examples of “buried fog.” A typical example is the fast-paced article that suddenly bursts into a sequence of four or five 30–50 word sentences.

And how about all those puffy quotes often included in merger announcements, financial results, appointments, and other corporate news releases. Why do we let many platitudes escape the editorial axe?

To help clear up foggy excesses, consider the following list of seven pitfalls that subject readers to long-sentence fatigue. If you avoid these bad habits, your endless-sentence disease may vanish.

1. The first sentence of an article is too long, exceeding 25 to 30 words. Reason: information overload.
2. Event identification and location lumped together requires too many words.
3. Long compound sentences are not immediately split during the editing process. Is there any excuse for that?
4. A long introductory clause traps the author into writing an even longer sentence.
5. Press release babble, especially within long quotes, is allowed to survive unedited.
6. A sentence including a direct quote cites the source’s name, company, and title (which may be a mouthful). A better way is to split attribution so that person’s name and company affiliation appear in one sentence. The full title (often overly long) appears in the next sentence.
7. Take a hard look at your website and magazine news intros. How many words appear before key story point is made? Too many ledes waste 20 or 30 words before the real story starts. Instead, the goal for ledes nowadays, especially in online news, should be no more than five words.

This article is adapted from “Tips for Better Editorial Content,” the appendix section of my book, Get Serious About Editorial Management. Other appendix topics include hiring efficiency, on-target headline writing, content diversity, ten common news pitfalls, on-target interviews, and editorial board feedback.