Reading Level Calculator
Measuring Text Difficulty Without a Human Reviewer
The Flesch-Kincaid formulas are among the oldest and most widely implemented readability metrics, originally developed for the US Navy to gauge whether technical manuals were readable by the sailors using them. They work on a simple premise: longer sentences and longer, multi-syllable words both make text harder to read, so counting words, sentences, and syllables in a passage is enough to estimate both a US school grade level and a 0–100 "reading ease" score.
The Formula
Flesch-Kincaid Grade Level = 0.39 × (Words / Sentences) + 11.8 × (Syllables / Words) − 15.59
Flesch Reading Ease = 206.835 − 1.015 × (Words / Sentences) − 84.6 × (Syllables / Words)
Flesch Reading Ease = 206.835 − 1.015 × (Words / Sentences) − 84.6 × (Syllables / Words)
Worked Example
A 120-word passage with 8 sentences and 170 syllables.
Words/Sentence = 120/8 = 15.0
Syllables/Word = 170/120 = 1.42
Grade Level = 0.39 × 15.0 + 11.8 × 1.42 − 15.59 = 5.85 + 16.76 − 15.59 = 6.98 → Grade 7.0
Reading Ease = 206.835 − 1.015 × 15.0 − 84.6 × 1.42 = 206.835 − 15.23 − 120.13 = 71.76
Syllables/Word = 170/120 = 1.42
Grade Level = 0.39 × 15.0 + 11.8 × 1.42 − 15.59 = 5.85 + 16.76 − 15.59 = 6.98 → Grade 7.0
Reading Ease = 206.835 − 1.015 × 15.0 − 84.6 × 1.42 = 206.835 − 15.23 − 120.13 = 71.76
| Reading ease score | Difficulty | Approximate US grade |
|---|---|---|
| 90 – 100 | Very Easy | 5th grade |
| 80 – 89 | Easy | 6th grade |
| 70 – 79 | Fairly Easy | 7th grade |
| 60 – 69 | Standard | 8th–9th grade |
| 50 – 59 | Fairly Difficult | 10th–12th grade |
| 30 – 49 | Difficult | College |
| 0 – 29 | Very Confusing | College graduate |
A reading ease of 71.76 falls in the "Fairly Easy" band, matching the grade-level estimate of about grade 7.
Where This Matters
- Writing for a target audience — content aimed at general readers is typically written for an 8th-grade level or below; checking a draft against this formula flags text that's unintentionally too dense.
- Textbook and curriculum selection — matching reading material to a specific grade band helps teachers choose texts that are challenging but not inaccessible.
- Plain-language compliance — government and healthcare documents are often required to meet a specific readability threshold; this formula is the most common way that requirement gets checked.
How to Use This Calculator
- Enter the total word count of the passage.
- Enter the total number of sentences.
- Enter the total number of syllables (count each word's syllables and sum them).
- Select Calculate to see the estimated grade level and reading ease score.
Related Calculations
For grade-level benchmarks by published reading range, see the Lexile Score Calculator.