Readability Score

Analyze text readability using Flesch-Kincaid, Gunning Fog, Coleman-Liau, and SMOG formulas.

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How it works

This tool calculates four widely used readability formulas to estimate the reading difficulty of your text. Each formula uses different textual features to produce a grade level or score.

• Flesch-Kincaid Grade Level: uses average sentence length and average syllables per word. The result is a U.S. school grade level (e.g., 8.0 means an 8th grader can understand the text). Formula: 0.39 × (words/sentences) + 11.8 × (syllables/words) − 15.59.
• Gunning Fog Index: factors in sentence length and the percentage of complex words (3+ syllables). The score approximates years of formal education needed to understand the text. Formula: 0.4 × [(words/sentences) + 100 × (complex words/words)].
• Coleman-Liau Index: uses character counts instead of syllables, making it easier to automate. It estimates the grade level from average letters and sentences per 100 words. Formula: 0.0588 × L − 0.296 × S − 15.8, where L and S are averages per 100 words.
• SMOG Index: estimates grade level based on the number of polysyllabic words (3+ syllables) across a sample of sentences. Requires at least 30 sentences for best accuracy. Formula: 3 + √(polysyllable count × 30 / sentences).

The overall grade level shown is the average of all four scores, giving a balanced estimate of the text's difficulty. All analysis runs entirely in your browser.

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