FleschKincaid

Flesch–Kincaid readability tests are two related measures used to assess the readability of English-language texts. They provide numeric scores based on sentence length and syllable density, intended to indicate how easy a passage is to read and what grade level a reader would likely need. The two components are the Flesch Reading Ease and the Flesch-Kincaid Grade Level.

Originating in mid-20th-century readability research, the Flesch Reading Ease score was developed by Rudolf Flesch. The Flesch-Kincaid Readability Tests were later developed by J. Peter Kincaid and colleagues to relate text difficulty to U.S. school grade levels. The tests are widely used in education, publishing, and software to gauge suitability of materials for particular audiences.

Calculation relies on two simple statistics: average sentence length (ASL) and average syllables per word (ASW). The Flesch Reading Ease score is 206.835 minus 1.015 times ASL minus 84.6 times ASW. The Flesch-Kincaid Grade Level score is 0.39 times ASL plus 11.8 times ASW minus 15.59.

Interpretation and use: Higher Reading Ease scores indicate easier text; higher Grade Level scores indicate more advanced material. The tests are commonly employed to tailor materials for students, evaluate document accessibility, and guide content development in publishing and software. They are most applicable to general English prose and rely on automatable syllable counting.

Limitations: The tests do not measure content quality, background knowledge, or vocabulary difficulty beyond syllable counts. They focus on English and may be less reliable for technical or literary texts. Syllable counting methods vary, and automated counts can produce different results across tools.