Readability is the ease with which a reader can understand a written text. It improves the quality of the text and makes it more accessible to readers. Factors like font choice, size, spacing, and other typographic elements impact how easy it is to read a text. Clear headings, bullet points, and other structural elements also help readers navigate and comprehend the content.
Why measuring readability matters
Readability matters a lot due to various reasons such as generating leads, engaging readers and clarity for the audience. It enhances the quality and makes the content understandable for those who find difficulty in perceiving the content.
Readable content is more likely to capture and retain the reader’s attention. When readers find the material understandable and engaging, they are more likely to stay on the page, read through the content, and remember the information.
Methods for measuring text readability
Following are some methods for measuring text readability.
1. Automated Readability Index (ARI)
The Automated Readability Index (ARI) was developed in 1967 by R.W. Senter and E.A. Smith for the U.S. Air Force. The main purpose was to evaluate the readability of lexicons and ensure that the instructions were easily understandable to readers.
Key Points:
- ARI focuses on the number of characters per word and words per sentence. This makes it particularly useful for evaluating texts where syllable counting might be impractical.
- The ARI produces a U.S. grade level score, indicating the minimum education level needed to understand the text.
How to Measure:
The ARI formula is:
4.71 x (characters/words) + 0.5 x (words/sentences) – 21.43.
Where;
- Characters: Total number of letters and digits in the text.
- Words: Total number of words in the text.
- Sentences: Total number of sentences in the text.
Grade Levels:
- An ARI score of 1 corresponds to first-grade reading level.
- An ARI score of 12 corresponds to twelfth-grade reading level.
- Higher scores indicate that higher levels of education are required to comprehend the text.
2. Coleman-Liau
The Coleman Liau Index was developed in 1975 by linguists Meri Coleman and T. L. Liau. It was designed to assess the readability of texts by analyzing the characters and sentence structures, providing a straightforward method to determine the reading grade level required to understand a piece of writing.
Key points:
The Coleman-Liau Index measures readability based on the number of letters in words and the average sentence length, rather than syllable counts.
How to Measure:
The Coleman-Liau Index formula is:
CLI = 0.0588L − 0.296S − 15.8
Where;
- L is the average number of letters per 100 words,
- S is the average number of sentences per 100 words.
Grade Levels:
- An index score of 1 corresponds to a first-grade reading level.
- An index score of 12 corresponds to a twelfth-grade reading level.
- Higher scores indicate that higher levels of education are required to comprehend the text.
3. Flesch-Kincaid Grade Level
The Flesch-Kincaid Grade Level formula was developed in the 1970s by J. Peter Kincaid and his team.
The goal was to create a reliable method for assessing the readability of technical documents and training. This readability formula has since become one of the most widely used and recognized tools for evaluating the complexity of English texts.
Key point:
- The Flesch-Kincaid Grade Level formula evaluates text readability based on the average number of syllables per word and the average number of words per sentence.
How to Measure:
The Flesch-Kincaid Grade Level formula is:
0.39 x (words/sentences) + 11.8 x (syllables/words) – 15.59.
Where;
- Words: Total number of words in the text.
- Sentences: Total number of sentences in the text.
- Syllables: Total number of syllables in the text.
Grade Levels:
- An FKGL score of 1 corresponds to a first-grade reading level.
- An FKGL score of 12 corresponds to a twelfth-grade reading level.
- Higher scores indicate that higher levels of education are required to comprehend the text.
4. Flesch Kincaid Reading Ease
The Flesch Reading Ease formula was developed by Rudolf Flesch in the 1940s. It was created to measure the readability of English texts, and make it easy to evaluate whether a piece of writing would be accessible to a broad audience.
Key points:
- The Flesch Reading Ease formula evaluates text readability based on the average number of syllables per word and the average number of words per sentence.
- It provides a score that ranges from 0 to 100, with higher scores indicating easier readability. A higher score means the text is easier to read, while a lower score indicates more complex text.
How to Measure:
The Flesch Reading Ease formula is:
206.835 – 1.015 x (words/sentences) – 84.6 x (syllables/words).
Where;
- Words: Total number of words in the text.
- Sentences: Total number of sentences in the text.
- Syllables: Total number of syllables in the text.
Reading Ease Scores:
- 90-100: Very easy to read, easily understood by an average 5th grader.
- 80-90: Easy to read, conversational English for consumers.
- 70-80: Fairly easy to read.
- 60-70: Plain English, easily understood by 13- to 15-year-old students.
- 50-60: Fairly difficult to read.
- 30-50: Difficult to read, best understood by college graduates.
- 0-30: Very difficult to read, best understood by university graduates.
5. Gunning Fog
The Gunning Fog Index was developed by Robert Gunning, an American businessman, in 1952. The aim of this is to improve the readability of newspapers and business documents, and make them more accessible to the public.
Key Points:
- The Gunning Fog Index evaluates text readability based on sentence length and the complexity of words.
How to Measure:
The Gunning Fog Index formula is:
0.4 [(words/sentences) + 100 (complex words/words)]
Where;
- Words: Total number of words in the text.
- Sentences: Total number of sentences in the text.
- Complex Words: Total number of complex words in the text (words with three or more syllables, excluding proper nouns, familiar jargon, and compound words).
Grade Levels:
- The score of fox index of 6 corresponds to sixth-grade reading level.
- The score of fox index of 12 corresponds to twelfth-grade reading level.
- Higher scores indicate that higher levels of education are required to comprehend the text.
6. LIX
The LIX, also known as the Last Barhet Index, was developed by Swedish scholar Carl-Hugo Bjornsson in the 1960s. It was created to measure the readability of texts in Swedish but has since been adapted for use in other languages, including English.
Key points:
- The LIX index evaluates text readability based on sentence length and word length.
- It provides a score that indicates the readability level of the text, with higher scores representing more difficult texts.
How to Measure:
The LIX formula is:
words /sentence +(long words /word x 100)
Where;
- Words: Total number of words in the text.
- Sentences: Total number of sentences in the text.
- Long Words: Total number of long words in the text (words with more than six characters).
LIX Scores:
- Below 25: Very easy to read, best for children.
- 25-30: Easy to read, suitable for teenagers.
- 30-40: Difficult to read, suitable for adult readers.
- 40-50: Difficult to read, best for academic papers.
- Above 50: Very difficult to read, suitable for technical or complex texts.
7. SMOG
The SMOG formula was created by G. Harry McLaughlin in 1969. It was developed to provide an accurate and easy-to-use method for determining the readability of texts.
This formula focuses on the number of complex words and aims to estimate the years of education required to understand a piece of writing.
Key point:
- The SMOG formula assesses readability based on the number of polysyllabic words (words with three or more syllables) in a text.
How to Measure:
The SMOG formula is:
SMOG Grade=1.0430 × (30× sentences polysyllabic words) ½ +3.1291
Where;
- Polysyllabic Words: Total number of words with three or more syllables.
- Sentences: Total number of sentences in the text.
Grade Levels:
- A SMOG grade of 6 corresponds to a sixth-grade reading level.
- A SMOG grade of 12 corresponds to a twelfth-grade reading level.
- Higher scores indicate that higher levels of education are required to comprehend the text.
A practical approach to readability
In practice we can use readability tools available online that automatically calculate these scores. The tools like Grammarly, Readability checker, and the Hemingway App can provide instant feedback, helping you to adjust your text for better readability.
Conclusion
By concluding, we get to know that selecting the right readability measurement method depends on your specific needs and the nature of your content.
For professional documents, ARI or Flesch-Kincaid might be suitable, while general content might benefit from the Flesch Reading Ease score.
For the most accurate assessment, consider using multiple readability formulas. Each method has its strengths and limitations, so combining them can provide a more comprehensive view of your text’s readability.
By understanding and applying these readability metrics, you can ensure your content is clear, engaging, and accessible to your target audience.