Readability Calculator

Paste any English text and this calculator scores how easy it is to read using six established formulas: Flesch Reading Ease, Flesch-Kincaid Grade Level, Gunning Fog, SMOG, Coleman-Liau and the Automated Readability Index. It also reports word and sentence counts, average sentence length and your longest sentences, which are usually the quickest thing to fix.

Scores update as you edit, so you can see the effect of shortening sentences or choosing simpler words. The text never leaves your browser.

Flesch Reading Ease = 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words)

Flesch-Kincaid Grade = 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59

Gunning Fog adds average sentence length to the percentage of words with three or more syllables and multiplies by 0.4. SMOG uses the count of polysyllabic words in 30 sentences. Coleman-Liau and ARI use letters per word instead of syllables, which makes them easy for computers to count. Higher Flesch Reading Ease means easier text; the other scores estimate the US school grade needed to understand it.

A passage of 100 words in 5 sentences with 140 syllables averages 20 words per sentence and 1.4 syllables per word. Flesch Reading Ease is 206.835 − 20.3 − 118.44 = 68.1, which is plain english, and the Flesch-Kincaid grade is 8.7, readable by most eighth or ninth graders.

For general public audiences, a Flesch Reading Ease of 60 or above, roughly eighth-grade level, is a common target. Health organizations often recommend writing patient materials at a sixth- to eighth-grade level, and the US Plain Writing Act of 2010 requires federal agencies to write clearly for the public. Technical and academic writing will naturally score lower, but even expert readers read faster when sentences are short and direct.

• One idea per sentence. If a sentence has two or more clauses joined by and, which or because, try splitting it.
• Choose shorter, familiar words. Use, not utilize; help, not facilitate; about, not approximately.
• Prefer active voice. "The team approved the plan" is shorter and clearer than "the plan was approved by the team".
• Cut filler. Phrases like in order to, at this point in time and due to the fact that can usually be one word.
• Use lists for steps and options instead of long sentences full of commas.

Readability research began in the 1920s with teachers trying to match books to students. Rudolf Flesch published his Reading Ease formula in 1948, and in 1975 the US Navy commissioned J. Peter Kincaid to convert it to a grade level for training manuals, which became the Flesch-Kincaid grade now built into many word processors. Insurance laws in several US states still require policies to meet a minimum Flesch score.

Formulas measure surface features, not meaning. A short sentence full of jargon can score well and still confuse readers, and a few long words that your audience knows well can lower a score unfairly. Syllable counts are estimated with rules that occasionally miss, and lists, headings and code can distort sentence counts, so analyze plain prose. Use the scores alongside other checks: ask whether a reader from your audience would understand each sentence on first reading.