Flesch Reading Ease Formula

What is the Flesch Reading Ease Formula?

The Flesch Reading Ease formula, developed by Rudolf Flesch in 1948, is one of the most trusted and widely used readability formulas. It calculates a score between 0 and 100 that indicates how easy or difficult a text is to read, with higher scores representing easier reading.

The Formula

The Flesch Reading Ease score is calculated using this formula:

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

Where:

• ASL = Average Sentence Length (total words ÷ total sentences)
• ASW = Average Syllables per Word (total syllables ÷ total words)

Score Interpretation

Flesch Reading Ease scores are interpreted as follows:

• 90-100: Very Easy (5th grade level) - Easily understood by an average 11-year-old student
• 80-89: Easy (6th grade level) - Conversational English for consumers
• 70-79: Fairly Easy (7th grade level) - Easily understood by 13- to 15-year-old students
• 60-69: Standard (8th-9th grade level) - Easily understood by 13- to 15-year-old students
• 50-59: Fairly Difficult (10th-12th grade level) - Fairly difficult to read
• 30-49: Difficult (College level) - Difficult to read, best understood by university graduates
• 0-29: Very Difficult (Graduate level) - Very difficult to read, best understood by university graduates

History and Development

Rudolf Flesch, an Austrian-American author and readability expert, developed this formula as part of his work on making written communication more accessible. The formula was refined through extensive testing with readers of various educational backgrounds and has become a standard in publishing, education, and content creation.

Applications

Content Marketing

Marketers use Flesch Reading Ease scores to ensure their content matches their target audience's reading level. Most successful web content scores between 60-70, making it accessible to the general public.

Education

Teachers and educational publishers use the formula to select age-appropriate reading materials and assess the difficulty of textbooks and assignments.

Government and Legal Documents

Many government agencies use Flesch Reading Ease to ensure public documents meet plain language requirements, typically targeting scores above 60.

Healthcare Communication

Medical professionals use the formula to create patient education materials that are easily understood, often aiming for scores of 60 or higher.

Advantages of the Flesch Reading Ease Formula

• Simplicity: Easy to calculate and understand
• Reliability: Extensively tested and validated
• Versatility: Applicable to various types of content
• Industry Standard: Widely recognized and accepted
• Quick Assessment: Provides immediate feedback on text difficulty

Limitations to Consider

• Surface-level Analysis: Only considers sentence length and syllable count
• Context Ignorance: Cannot assess conceptual difficulty or prior knowledge requirements
• Cultural Factors: Doesn't account for cultural relevance or familiarity
• Text Type Variations: May not be accurate for poetry, dialogue, or technical specifications

Improving Your Flesch Reading Ease Score

Shorten Sentences

Break long, complex sentences into shorter, more digestible ones. Aim for an average of 15-20 words per sentence.

Use Simpler Words

Replace multi-syllable words with shorter alternatives when possible:

• "Utilize" → "Use"
• "Demonstrate" → "Show"
• "Facilitate" → "Help"
• "Approximately" → "About"

Active Voice

Use active voice instead of passive voice to create shorter, clearer sentences.

Eliminate Unnecessary Words

Remove redundant phrases and filler words that don't add meaning to your content.

Industry Benchmarks

Different industries and content types have different target scores:

• News Articles: 60-70 (8th-9th grade level)
• Marketing Copy: 60-80 (6th-9th grade level)
• Academic Papers: 30-50 (College level)
• Children's Books: 80-100 (Elementary level)
• Technical Manuals: 40-60 (High school to college level)
• Legal Documents: 50-70 (Plain language initiatives)

Using Flesch Reading Ease with Other Metrics

While the Flesch Reading Ease score is valuable, it's most effective when used alongside other readability metrics:

• Flesch-Kincaid Grade Level: Provides specific grade level equivalents
• Gunning Fog Index: Focuses on complex words and sentence structure
• SMOG Index: More accurate for longer texts
• User Testing: Real-world feedback from your target audience

By combining multiple readability measures with qualitative assessment, you can create content that truly resonates with your intended readers.