What Is Readability and How to Measure It?

Zhai Yujing (翟玉净)

(The Institute of Online Education, Beijing Foreign Studies University)

Abstraction

This article outlines the subject of ‘readability’ and its relevance to reading materials. The paper starts with some facts to show you the significance of knowing the concept of ‘readability’. Then, details, including its definition and historical overview are explicated to further your understanding of ‘readability’. Next, the author moves on to the focus of this paper－readability formulas, which refer to the methods writers or educators can use to assess and determine the reading levels of the materials. Finally, this paper concludes with some suggestions on using readability formulae scientifically that will help to increase the readability level.

1. Introduction

A true story …

“The CEO of a firm that manufactures electronic controls asked me (Leon Fletcher) to rewrite the instruction manual for his product. At a meeting of his executives, I asked, “Are you sure your controls work — have you tested them?”

They bristled at that question, understandably. They roared, “Of course we test every one of them!” My reply: “Good. And have you tested your instruction manual?”

They had not. The manual was written by a manager, reviewed by engineers, approved by sales. It required the reading skills of a college senior, according to my readability study. But the manual was intended for use by unskilled laborers, most with only fifth grade educations.”

Some other facts …

l More than one out of four cancer patients were not able to understand any of 30 booklets produced by the American Cancer Society, according to a 1995 study by Villanova University.

l The catalog of one California community college stated its “General Education Requirements” — essential information for students just out of high school — in text that required reading skills beyond those of a Ph.D.

l Three out of four adults 60 years and older find it “hard to understand” most information in newspapers, said a study by the Federal Drug Administration.

l It was not long ago (i.e., in 1994) that the results from the "Adult Literacy in America" study (accomplished by the Educational Testing Service for the U.S. Government; which studied 26,000 adults) were announced a surprising number of college graduates were found to only read at less than college levels.

The above facts prove that ‘readability’ is severely neglected by some writers and educators. Some experts recommend that any written composition/document that is utilized, via reading, to communicate necessary details to individuals be very carefully examined with respect to its readability level. To expect an individual to comprehend or otherwise understand a written communication that requires reading skills beyond that possessed by the involved individual can be a very major error. Therefore, this paper focuses on ‘readability formula’ which is a very effective way to help you to assess the readability level of the texts you write or select for your readers.

2. Readability and Readability Formula

2.1 Definition

In the broadest sense, ‘readability’ is the sum total (including interactions) of all those elements within a given piece of printed material that affect the success which a group of readers have with it (Dale & Chall, 1948). The success is the extent to which they understand it, read it at optimum speed, and find it interesting.

A more reasonable definition of ‘readability’ that is in keeping with more recent research and theory is the level of ease or difficulty with which text can be understood by a particular reader who is reading that text for a specific purpose.

The purpose of readability assessment is to effect a ‘best match’ between intended readers and texts. Readability tests, which are mathematical formulas, were designed to assess the suitability of reading materials for readers at particular grade levels or ages. These readability formulas are the most widely used methods for predicting text difficulty. A readability formula or index ‘is like a yardstick that help us measure certain qualities in the writing so we can make objective judgements about reading level’ (Laubach & Koschnick, 1977, p.12).

2.2 A brief historical overview of ‘Readability Formula’

According to Timothy D. Giles, Talmudic priests in the 10th century C.E. employed a kind of readability formula, calculating ordinary and abstract meanings using word and idea tallies. These calculations were developed because the priests were concerned that their meanings would be clearly and precisely understood.

Modern research into readability formula began in 1921 when Thorndike published The Teacher’s Word Book in which he tabulated words according to the frequency of their use in general literature. The book is really worth mentioning because it provided a means for measuring the difficulty of words and permitted the development of mathematical formula. Since then, the research on readability formula started to develop rapidly. During 1920’s, research activities concentrated on looking for word factors that could be used to predict readability. Research broadened during the 1930’s and throughout the 1940’s, deriving formulas that could accurately predict readability using the least number of factors.

3. Popular ‘Readability Formulas’

3.1 Review

By 1973 more than 200 language variables had been tried in almost 200 different readability formulas, but the vast majority of these formulas are no longer in use. Today there are by now dozens of readability formulas in existence, but for general use there are only a handful to choose from. They fall into two groups－those based on sentence length and a word list and those based on sentence length and word length. Put another way, readability formulas are usually based on one semantic (the difficulty of words) and one syntactic factor (the difficulty of sentences). Words are either measured against a frequency list or are measured according to their length in characters or syllables. Sentences are measured for the average length in characters or words. Studies have confirmed that counting more things does not make the formula any predictive of reading ease but takes a lot more effort.

Readability tests can be performed manually by counting and doing a mathematical calculation, or be referring to a chart or graph. They also can be performed by computer. Most grammar or editing software today can perform several readability tests.

3.2 General principles

Before using a readability formula, you’d better go through the following principles first:

1) When counting syllables for these tests, it helps to say the words aloud.

Some examples of syllables count are: another (3), area (3), passed (1), surface (2), surfaces (3), particle (3), enable (3).

2) When counting numbers, symbols, initials, etc, count one syllable for each number or letter. For example: 1998 = 4 syllables (1-9-9-8), 4.2 = 3 syllables (4-point –2), H2O = 3 syllables (H-2-O), USA = 3 syllables (U-S-A), Fig. 2 = 2 syllables (Fig-two)

3) For abbreviations (cm, mm, km, kg. eg, ie), the usual rule is to count each as just one syllable. Since headings and sub-headings are usually not sentences, they are best ignored. It is not known how to deal with a formula or a numerical calculation, so for the results below they were just ignored.

3.3 Some widely recognized readability formulas

3.3.1 Fry Readability Graph

Fry developed a ‘Readability Graph’ in 1965 for predicting readability. He used the common formula variables of syllables per 100 words and words per sentence. The user marks the counts of the variables on a graph and then reads the readability grade score directly from it.

When you refer to Fry Readability Graph, follow the steps below:

Step1. Select samples of 100 words.

Step2. Find y, the average number of sentences per 100-word passage (calculating to the nearest tenth.

Step3. Find x, the average number of syllables per 100-word sample.

Step4. Use the Fry graph to determine the reading age, in years or grade level.

The curve represents normal texts. Points below the curve imply longer than average sentence length. Points above the curve represent text with a more difficult vocabulary (as in school science texts).

This text is suitable for all ages, from infant to upper secondary.

Sentences per 100 words (graph vertically):

Syllables per 100 words (graph horizontally):

3.3.2 The Flesch Reading Ease Formula

Flesch published his formula in 1943. In designing it for general adult reading matter, he felt it gave proper attention to abstract words as well as sentence length. The formula uses four factors: number of syllables per 100 word, average number of words per sentence, number of personal words per 100 words, and number of personal sentences per 100 sentences.

The output of the Flesch Reading Ease formula is a number from 0 to 100, with a higher score indicating easier reading. For example, zero means practically unreadable and 100 means extremely easy. The minimum score for plain English is 60, or about 20 words per sentence and 11/2 syllables per word.

Step 1. Count the words.

Count the words in your piece of writing. Count as single words contractions, hyphenated words, abbreviations, figures, symbols and their combinations, e.g., wouldn't, full-length, TV, 17, &, $15, 7%.

Step 2. Count the syllables.

Count the syllables in your piece of writing. Count the syllables in words as they are pronounced. Count abbreviations, figures, symbols and their combinations as one-syllable words. If a word has two accepted pronunciations, use the one with fewer syllables. If in doubt, check a dictionary.

Step 3. Count the sentences.

Count the sentences in your piece of writing. Count as a sentence each full unit of speech marked off by a period, colon, semicolon, dash, question mark or exclamation point. Disregard paragraph breaks, colons, semicolons, dashes or initial capitals within a sentence. For instance, count the following as a single sentence:

You qualify if —

(1) you are at least 58 years old; and

(2) your total household income is under $5,000.

Step 4. Figure the average number of syllables per word.

Divide the number of syllables by the number of words.

Step 5. Figure the average number of words per sentence.

Divide the number of words by the number of sentences.

Step 6. Find your readability score.

Find the average sentence length and word length of your piece of writing on the chart (below). Take a straightedge or ruler and connect the two figures. The intersection of the straightedge or ruler with the center column shows your readability score.

Here are the scores of some popular reading materials. These are average scores of random samples.

Comics	92
Consumer ads in magazines	82
Movie Screen	75
Seventeen	67
Reader's Digest	65
Sports Illustrated	63
New York Daily News	60
Atlantic Monthly	57
Time	52
Newsweek	50
Wall Street Journal	43
Harvard Business Review	43
New York Times	39
New York Review of Books	35
Harvard Law Review	32
Standard auto insurance policy	10
Internal Revenue Code	Minus 6

Here's how the scores translate into school grades. Reading matter with the score shown on the left side will be easy for students on the level shown on the right.

Score	School Level
90 to 100	5th grade
80 to 90	6th grade
70 to 80	7th grade
60 to 70	8th and 9th grade
50 to 60	10th to 12th grade (high school)
30 to 50	College
0 to 30	College graduate

Besides the chart, you can also use an algorithm to get Flesch Reading Ease score. It reads as follows:

206.835 – (1.015 × ASL) – (84.6 × ASW)

Where:

ASL = average sentence length (the number of words divided by the number of sentences)

ASW = average number of syllables per word (the number of syllables divided by the number of words)

3.3.3 Flesch-Kincaid Readability Ease Formula

Flesch-Kincaid Grade Level, which is like Flesch Reading Ease, is based on the average number of syllables per word and words per sentence. The Flesch-Kincaid Grade Level score rates text based on the U.S. high school grade level system (i.e. a score of 7.0 would mean a 7th grader should be able to comprehend the text). The Flesch Reading Ease score is based on a 100 point scale; the higher the score, the easier it is to comprehend.

The following is the algorithm to determine the Flesch-Kincaid grade level:

1. Calculate the average number of words you use per sentence, ASL.

2. Calculate the average number of syllables per word, ASW.

3. Multiply the average number of words by 0.39 and add it to the average number of syllables per word multiplied by 11.8.

4. Subtract 15.59 from the result.

Algorithm: (0.39 × ASL) + (11.8 ×ASW) － 15.59

A score of 8.0 means that an eighth grader can understand the document. For most standard documents should aim for a score of approximately 7.0 to 8.0.

3.3.4 McLaughlin ‘SMOG’ Formula

The SMOG Readability Formula, adapted from McLaughlin, G. (1969) is a simple method you can use to determine the reading level of your written materials. To calculate the SMOG (Simplified Measure of Gobbledygoop) reading grade level, begin with the entire written work that is being assessed, and follow these four steps:

1. Count off 10 consecutive sentences near the beginning, in the middle, and near the end of the text.

2. From this sample of 30 sentences, circle all of the words containing three or more syllables (polysyllabic), including repetitions of the same word, and total the number of words circled.

3. Estimate the square root of the total number of polysyllabic words counted. This is done by finding the nearest perfect square, and taking its square root.

4. Finally, add a constant of three to the square root. This number gives the SMOG grade, or the reading grade level that a person must have reached if he or she is to fully understand the text being assessed.

A few guidelines will help to clarify these directions:

Ø A sentence is defined as a string of words punctuated with a period (.), an exclamation point (!) or a question mark (?).

Ø Hyphenated words are considered as one word.

Ø Numbers which are written out should also be considered, and if in numeric form in the text, they should be pronounced to determine if they are polysyllabic.

Ø Proper nouns, if polysyllabic, should be counted, too.

Ø Abbreviations should be read as unabbreviated to determine if they are polysyllabic.

Not all pamphlets, fact sheets, or other printed materials contain 30 sentences. To test a text that has fewer than 30 sentences:

1. Count all of the polysyllabic words in the text.

2. Count the number of sentences.

3. Find the average number of polysyllabic words per sentence as follows:

Average= Total # of polysyllabic words/Total # of sentences

4. Multiply that average by the number of sentences short of 30.

5. Add that figure on to the total number of polysyllabic words.

6. Find the square root and add the constant (常数, 恒量) of 3.

A quick version of the SMOG test:

Count the number of polysyllabic words in the chain of 30 sentences and look up the approximate grade level on the SMOG conversion table.

SMOG Conversion Table

Total polysyllabic word counts	Approximate grade level (+/- 1.5 grades)
0-2	4
3-6	5
7-12	6
13-20	7
21-30	8
31-42	9
43-56	10
57-72	11
73-90	12
91-110	13
111-132	14
133-156	15
157-182	16
183-210	17
211-240	18

Sample:

In Controlling Cancer—You Make a Difference

The key is action. You can help protect yourself against cancer. Act promptly to:

Prevent some cancers through simple changes in lifestyle.

Find out about early detection tests in your home.

Gain peace of mind through regular medical checkups.

Cancers You Should Know About

Lung Cancer is the number one cancer among men, both in the number of new cases each year (79,000) and deaths (70,500). Rapidly increasing rates are due mainly to cigarette smoking. By not smoking, you can largely prevent lung cancer. The risk is reduced by smoking less, and by using lower tar and nicotine brands. But quitting altogether is by far the most effective safeguard. The American Cancer society offers Quit Smoking Clinics and selfhelp materials.

Colorectal Cancer is second in cancer deaths (25,100) and third in new cases (49,000). When it is found early, chances of cure are good. A regular general physical usually includes a digital examination of the rectum and a guaiac slide test of a stool specimen to check for invisible blood. Now there are also Do-It-Yourself Guaiac Slides for home use. Ask your doctor about them. After you reach the age of 40, your regular check-up may include a “Procto,” in which the rectum and part of the colon are inspected through a hollow, lighted tube.

Prostate Cancer is second in the number of new cases each year (57,000), and third in deaths (20,600). It occurs mainly in men over 60. A regular rectal exam of the prostate by your doctor is the best protection.

A Check-Up Pays Off

Be sure to have a regular, general physical including an oral exam. It is your best guarantee of good health.

How Cancer Works

If we know something about how cancer works, we can act more effectively to protect ourselves against the disease. Here are the basics:

1. Cancer spreads; time counts—Cancer is uncontrolled growth of abnormal cells. It begins small and if unchecked, spreads. If detected in an early, local stage, the chances for cure are best.

2. Risk increases with age—This is not a reason to worry, but a signal to have more regular, thorough physical check-ups. Your doctor or clinic can advise you on what tests to get and how often they should be performed.

3. What you can do—don’t smoke and you will sharply reduce you chances of getting lung cancer. Avoid too much sun, a major cause of skin cancer. Learn cancer’s Seven Warning Signals, listed on the back of this leaflet, and see your doctor promptly if they persist. Pain is usually a late symptom of cancer; don’t wait for it.

Know Cancer’s Seven Warning Signals

1. Change in bowel or bladder habits.

2. A sore that does not heal.

3. Unusual bleeding or discharge.

4. Thickening or lump in breast or elsewhere

5. Indigestion or difficulty in swallowing

6. Obvious change in wart or mole

7. Nagging cough or hoarseness

If you have a warning signal, see your doctor.

Unproven Remedies

Beware of unproven cancer remedies. They may sound appealing, but they are usually worthless. Relying on them can delay good treatment until it is too late. Check with your doctor or the American Cancer Society.

More Information

For more information of any kind about cancer--free of cost--contact your local unit of the American Cancer Society

We have calculated the reading grade level for this example.

Compare your results to ours, and then check both with the SMOG conversion table:

Readability Test Calculations