Readability Checker

Every score here is a published formula fed with three counts: sentences, words and syllables. Flesch Reading Ease is 206.835 − 1.015 × (words ÷ sentences) − 84.6 × (syllables ÷ words): long sentences and long words both pull it down, and higher means easier. The Flesch-Kincaid Grade Level uses the same two inputs, 0.39 × (words ÷ sentences) + 11.8 × (syllables ÷ words) − 15.59, and gives a number that corresponds with a US school grade.

The Gunning Fog Index is 0.4 × (words ÷ sentences + 100 × complex words ÷ words). A complex word has three or more syllables, not counting names, hyphenated compounds, or -es, -ed and -ing as a syllable. The SMOG grade is 1.0430 × √(words of three or more syllables × 30 ÷ sentences) + 3.1291; it was normed on samples of 30 sentences, so with a shorter text the page says the grade is a rough guide.

Sentences are split with the Sentence Counter's rules and syllables are counted with the Syllable Counter's rules. Syllable counts in English are a close estimate, not a dictionary lookup, so a score can differ a little from another checker that counts syllables differently.

Flesch Reading Ease runs from about 100 (very easy, 5th grade) down to 0 and below. On the standard table 70-80 is fairly easy (7th grade), 60-70 is plain English that 13- to 15-year-olds understand easily, 50-60 is fairly difficult (10th-12th grade), 30-50 is difficult (college) and below 30 very difficult. Reader's Digest scores about 65 and Time about 52.

The Flesch-Kincaid grade, the Gunning Fog Index and SMOG are all US school grades. Texts for a wide audience generally need a Fog index under 12, and Pennsylvania was the first US state to require that car insurance policies be written at no higher than a ninth-grade level by the Flesch-Kincaid formula.

No score is good or bad on its own: the right range depends on who reads. A buyer skimming on a phone and a specialist reading a technical report need different texts. Use the scores to compare two drafts of the same text, and the marked sentences to find where to start.

The formulas weigh the same text differently. Flesch and Flesch-Kincaid look at average sentence length and average syllables per word. Gunning Fog looks at sentence length and the share of words with three or more syllables, and leaves out names. SMOG looks only at the long words per sentence. A text of short sentences with many technical terms can look easy to Flesch and hard to SMOG.

Each formula also has its own scale, so the grades rarely match exactly. Read them together: when all of them move the same way after an edit, the text really got easier.

Busy readers skim. A follow-up email after a sales call, a proposal summary or a press release that reads at a plain-English level gets its point across before the reader moves on. Paste the draft, look at the marked sentences, split the longest one and swap a long word for a short one, then watch the scores move.

The same check helps with staff training notes, onboarding guides, handouts and reports: anything written for many readers with different backgrounds. School writing works too, but a teacher's own rubric comes first.

Switch the language above the text and the checker uses formulas made for that language. German texts get Amstad's Flesch formula, 180 − words per sentence − 58.5 × syllables per word, on the usual 0-100 Flesch scale, and the first Wiener Sachtextformel, a school grade from 4 (very easy) to 15 (very hard) built from long words, sentence length and one-syllable words.

Spanish texts get the Flesch-Szigriszt index (Szigriszt-Pazos), 206.835 − 62.3 × (syllables ÷ words) − (words ÷ sentences), read on the INFLESZ scale: below 40 very difficult, 40-55 somewhat difficult, 55-65 normal, 65-80 quite easy and above 80 very easy. The study behind INFLESZ found health information more likely to be read and understood above 55.