Reading Level Calculator Formula

Understand the math behind the reading level calculator. Each variable explained with a worked example.

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Formulas Used

Grade Level

grade_level = 0.39 * avg_sentence_len + 11.8 * avg_syllables - 15.59

Flesch Reading Ease

reading_ease = 206.835 - 1.015 * avg_sentence_len - 84.6 * avg_syllables

Rounded Grade Level

rounded_grade = round(0.39 * avg_sentence_len + 11.8 * avg_syllables - 15.59)

Variables

VariableDescriptionDefault
avg_sentence_lenAverage Sentence Length (words)15
avg_syllablesAverage Syllables per Word1.5

How It Works

How to Calculate Reading Level

The Flesch-Kincaid Grade Level formula estimates the U.S. school grade needed to understand a text.

Formula

Grade Level = 0.39 x ASL + 11.8 x ASW - 15.59

Where ASL = Average Sentence Length, ASW = Average Syllables per Word.

Lower grade levels mean easier text. A grade level of 8 means an 8th grader can understand it.

Worked Example

A text has an average sentence length of 15 words and 1.5 syllables per word.

avg_sentence_len = 15avg_syllables = 1.5
  1. 01Grade level = 0.39 x 15 + 11.8 x 1.5 - 15.59
  2. 02= 5.85 + 17.7 - 15.59 = 7.96
  3. 03Rounded grade level = 8
  4. 04This text is at an 8th-grade reading level.

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