Readability Score Calculator

The Flesch Reading Ease score rates text on a scale from 0 to 100, where higher scores indicate easier reading. Scores of 60–70 are considered standard (plain English), while scores below 30 are very difficult (best for academic and professional audiences). Most general-audience writing should aim for a score of 60 or above.

The Flesch-Kincaid Grade Level is calculated using the formula: 0.39 × (Total Words / Total Sentences) + 11.8 × (Total Syllables / Total Words) − 15.59. The result corresponds to a U.S. school grade level, so a score of 8 means the text is appropriate for an 8th-grade reading level.

The Gunning Fog Index estimates the years of formal education needed to understand a piece of text on first reading. It is calculated as 0.4 × ((words/sentences) + 100 × (complex words/words)), where complex words are those with three or more syllables. A score of 12 corresponds to a U.S. high school senior level.

The Coleman-Liau Index uses characters per word and sentences per word (rather than syllables) to estimate the U.S. grade level required to comprehend a text. The formula is: 0.0588 × L − 0.296 × S − 15.8, where L is the average number of letters per 100 words and S is the average number of sentences per 100 words.

It depends on your target audience. For general web content and blog posts, a Flesch Reading Ease of 60–70 and a grade level of 7–8 is ideal. Academic or technical writing can have lower ease scores. Newspaper writing typically targets a grade level of 8–10, while children's books aim for grade levels of 3–6.

For reliable results, your text should contain at least 100 words and several complete sentences. Very short texts (fewer than 30 words or just 1–2 sentences) can produce skewed or misleading scores because the statistical formulas are designed for larger samples of text.

Readability scores primarily measure sentence length and word complexity (syllable count or character count), not the semantic difficulty of concepts. A text full of short, uncommon jargon words might score 'easy' despite being conceptually hard. Use readability scores as a guide alongside content clarity reviews.

No single formula is universally best — each was developed for different contexts. The Flesch Reading Ease and Flesch-Kincaid Grade Level are the most widely used for general English text. The Gunning Fog Index is popular in journalism, while the Coleman-Liau Index works well for texts where syllable counting is difficult. Comparing all four gives a more complete picture.