We can dissect the term "readability" into "read" + "ability," which translates into the ability to read. Readability has nothing to do with either legibility or literacy. In fact, readability is more of a judgmental exercise for the targeted audience. George Klare (1963) defines readability as "the ease of understanding or comprehension due to the style of writing." We can consider readability as means to measure the difficulty of text or page layout, so the writer knows how effectively his text will reach his target audience before he publishes or distributes it.

We can assess readability through readability tests by applying readability formulas. Readability formulas are mathematical in nature; each formula's primary aim is to measure the grade level a person must have to read and comprehend a text. Writers consider readability formulas as simple ways to judge read-ability, i.e., the difficulty level of a text.

Readability formulas measure certain features of a text based on mathematical calculations. We base these readability measures on a handful of factors; the most common factors include the number of words in a sentence, as well as the number of letters or syllables per word. Most readability formulas are based on one semantic factor (i.e., the difficulty of words), and one syntactic factor (i.e., the difficulty of sentences). We don't need to calculate other factors, as they tend to make the formulas more complex and achieve little in return.

Another fact about these formulas is that you don't need readers to read out (or try to read out) the text. However, readability formulas don't always work with 100% accuracy.

Importance of Readability Formulas

It requires a great deal of effort to come up with some kind of text. This text may be unique in its contents, yet it fails to serve its purpose of making the reader understand and use it. The problem many writers face is how to assess the "readability" of their text. Readability formulas offer the solution. By applying these scientific and mathematical principles, the readability formulas aim to present an objective analysis about the readability of a particular text.

Commonly Used Readability Formulas

Researchers and writers have been using readability formulas since 1920 and, over the years, they have spent a lot of time devising the most accurate and scientific formulas to assess readability. Some of the popular and commonly used formulas include:

1. Rudolph Flesch's Reading Ease Formula;

2. Flesch's Grade Level;

3. J. Peter Kinkaid's Flesch-Kinkaid Index;

4. Robert Gunning's Fog Index;

5. The SMOG Readability Formula;

6. Fry's Readability Graph;

7. New Dale-Chall Formula;

8. Powers-Sumner-Kearl Readability Formula;

9. FORCAST Readability Formula; and

10. Spache Readability Formula.

Why Use Readability Formulas?

Despite their much-criticized shortcomings, many organizations consider readability formulas an important tool to evaluate the readability of text. Here are reasons why you should use readability formulas:

1. Most Americans have limited reading ability, which means their reading grade-level balances between average and poor. It makes sense to prepare text in plain English if your readers have limited reading capabilities. How do you determine if your text is readable from your readers' point of view? Simple. Use readability formulas.

2. If the text is not readable, the purpose of writing it in the first place gets defeated. For instance, let's assume you've written an instruction manual for your employees. If your employees cannot read this manual, they will never understand the true meaning of its contents; this will adversely impact their productivity. Using readability formulas can prevent such a scenario and tell you beforehand if your text is of any value to your employees.

3. Readability formulas help you to prepare a readable text. In other words, these formulas can save you time and money that you might have wasted in writing a complicated document, which is not useful for the target audience.

4. Just imagine how frustrated your target audience feels trying to read an ill-prepared document. Studies show that enforcing difficult text can have adverse effects on the overall mood and psychology of your customers. They may feel confused by a clumsily prepared text and opt for another provider.

5. Preparing text costs money. If you produce an unreadable text, you are increasing your organization's operating costs. By using readability formulas, you are almost 80% sure that your readers find your text useful; thereby, keeping your costs down.

6. Most reputable word-processors, like MS-Word, have a built-in readability formula feature that helps you to assess the readability of a document. If you can gain such a useful insight into the document without manually calculating the readability, why won't you use it?

The underlying message of each formula is the same: if you use shorter, average sentence lengths and fewer big-lettered words, you can reduce the reading level and increase the speed and ease of reading.