The Flesch Index Calculator measures how easy or difficult a text is to read. It calculates a readability score based on the length of sentences and the complexity of words. This tool is valuable for writers, educators, marketers, and developers who need to ensure their content is understandable to their target audience.
Using this calculator, you can quickly assess whether your text is suitable for children, teens, or adults with advanced reading skills. It supports educational standards, content grading, and user experience optimization on websites and printed materials.
Formula of Flesch Index Calculator
Flesch Index = 206.835 − (1.015 × ASL) − (84.6 × ASW)
Where:
- ASL is the Average Sentence Length, calculated by dividing the total number of words by the total number of sentences.
- ASW is the Average Syllables per Word, calculated by dividing the total number of syllables by the total number of words.
Step-by-step:
- Count total words in the text.
- Count total sentences.
- Count total syllables.
- Compute ASL = Total Words ÷ Total Sentences.
- Compute ASW = Total Syllables ÷ Total Words.
- Insert both values into the formula above.
The result is a Flesch Reading Ease Score.
Readability Score Table
| Score Range | Description | Grade Level Approximation |
|---|---|---|
| 90–100 | Very Easy | 5th grade or below |
| 80–90 | Easy | 6th grade |
| 70–80 | Fairly Easy | 7th grade |
| 60–70 | Standard | 8th–9th grade |
| 50–60 | Fairly Difficult | 10th–12th grade |
| 30–50 | Difficult | College level |
| 0–30 | Very Difficult | College graduate and above |
This table helps writers adjust their tone and complexity depending on their readers’ comprehension level.
Example of Flesch Index Calculator
Suppose a text contains:
- 120 words
- 5 sentences
- 180 syllables
Step 1: ASL = 120 ÷ 5 = 24
Step 2: ASW = 180 ÷ 120 = 1.5
Step 3: Apply formula:
Flesch Index = 206.835 − (1.015 × 24) − (84.6 × 1.5)
Flesch Index = 206.835 − 24.36 − 126.9
Flesch Index ≈ 55.57
This indicates the text is fairly difficult, typically suitable for high school students.
Most Common FAQs
A: A score between 60 and 70 is considered standard and readable by most teenagers and adults. Higher scores are easier to read, while lower scores are more complex.
A: Yes, it is commonly used to evaluate academic papers to ensure they are clear and concise. However, academic writing may intentionally use a more complex structure depending on the target audience.
A: No, the Flesch Index is designed specifically for English. Other languages may use adapted readability formulas due to different sentence structures and syllabic characteristics.