Flesch reading ease: what your score means

Flesch reading ease is a score, usually between 0 and 100, that rates how easy a passage of English is to read. It is built from two numbers, the average words per sentence and the average syllables per word, and higher means easier. A score of 60 to 70 is plain English most adults read in one pass, below 30 reads like an academic journal, and 90 or more reads like a children's book. It measures length and nothing else, so use it to find heavy passages, not to decide whether the writing is good.

The Flesch reading ease formula

Rudolf Flesch published the formula in 1948 in the Journal of Applied Psychology, in a paper titled "A new readability yardstick". Checkers still use the same constants.

Flesch reading ease = 206.835 - 1.015 × (words / sentences) - 84.6 × (syllables / words)

Look at the two weights. Each extra word in the average sentence costs about one point. Each extra syllable in the average word costs 84.6 points, so moving from 1.5 to 1.6 syllables per word costs 8.5 points, as much as adding eight words to every sentence. That is why a page of medium-length sentences full of abstract nouns can score worse than a page of long, plain sentences.

The 0 to 100 range is a convention. A text made only of one-word sentences with one syllable scores 121.2, and one long sentence of four- and five-syllable words drops below zero.

Flesch reading ease score table

Each band of the Flesch reading ease score lines up with a US school level.

For calibration, the Wikipedia article on the test puts Reader's Digest at about 65, Time magazine at about 52 and the Harvard Law Review in the low 30s.

Flesch-Kincaid grade level and how it relates

The Flesch-Kincaid grade level runs the same two averages through different weights and returns a US school grade, so 8.0 means a typical eighth grader can follow the text.

Flesch-Kincaid grade level = 0.39 × (words / sentences) + 11.8 × (syllables / words) - 15.59

J. Peter Kincaid and three colleagues derived it in 1975 for the US Navy. They tested 531 enlisted personnel at four Navy technical schools on 18 passages from Navy training manuals, then recalculated Flesch's formula to predict a reading grade. Per Wikipedia, the Army first used it to rate technical manuals in 1978, and it soon became a US military standard.

The two scores move in opposite directions, and you cannot convert one into the other. In reading ease, one more syllable per word costs as much as 83 more words per sentence. In the grade formula it equals about 30 more words, so long sentences count for relatively more. Two texts can share a reading ease score and sit grades apart.

Text A uses short words in long sentences. Text B uses longer words in short sentences. Reading ease calls them equal, and the grade level puts B two and a half grades lower. When you report to a client, give the grade. "Grade 8" means something to people outside SEO. "68.1" does not.

Before and after: a rewrite with the scores worked out

Here is a typical help-page paragraph.

If you are experiencing difficulties signing in, the support team will investigate the configuration of your account and provide additional assistance. Response times vary depending on the complexity of the issue.

It has 31 words in 2 sentences, and 62 syllables by a dictionary count.

Reading ease = 206.835 - 1.015 × (31 / 2) - 84.6 × (62 / 31) = 21.9
Grade level  = 0.39 × (31 / 2) + 11.8 × (62 / 31) - 15.59     = 14.1

The sentences are not the problem, since 15.5 words is an ordinary length. Seven words do the damage. Experiencing, difficulties, investigate, configuration, additional, assistance and complexity hold 29 of the 62 syllables.

The rewrite keeps the meaning and swaps the words.

If you can't sign in, contact the support team. They will check your account settings and help you fix the problem. Complex problems take longer to solve.

Reading ease = 206.835 - 1.015 × (27 / 3) - 84.6 × (35 / 27) = 88.0
Grade level  = 0.39 × (27 / 3) + 11.8 × (35 / 27) - 15.59     = 3.2

The score rose 66.1 points. Shorter sentences account for 6.6 of them and shorter words for 59.5, so splitting the sentences alone would have bought less than 7 points here. The rewrite also opens with what the reader should do, which no formula rewards.

Paste the first version into our analyzer and you get 24.6, not 21.9, because its syllable counter scores "experiencing" as four syllables instead of five. Every readability checker estimates syllables its own way. Track one tool's score over time, and never compare a 62 from one checker with a 65 from another.

What a readability score cannot see

Flesch reading ease counts syllables, words and sentences. Anything that takes understanding is invisible to it.

Jargon made of short words. "Rebase the fork, then squash the commits." scores 91, very easy. A developer reads it instantly and a marketing manager learns nothing. Acronyms slip through too. A vowel-group counter scores "TTL" as one syllable, while a reader hears three letters and may not know what any of them stand for.

Structure. The formula works on totals, so shuffling every sentence on a page leaves the score unchanged. It cannot tell whether the answer is in the first line or the ninth paragraph, or whether five steps would read better as a numbered list.

Facts. "Google ranks pages by their Flesch score." also scores above 90, and it is false.

Precise long words. In a security guide, authentication and authorization are different things, and each has five syllables. Replacing both with "sign-in" lifts the score and blurs the difference the reader came to learn.

Does readability affect SEO?

Not through a formula. Google has not said it scores pages with Flesch or any other readability formula, and its guide to creating helpful, reliable, people-first content never mentions a readability score.

What the guide asks for reads like an editor's checklist. One of its questions is "Does the content have any spelling or stylistic issues?" Another asks whether the content looks well produced or sloppy and hastily made. It names clear writing as one sign of the skill that gives visitors a satisfying experience, and it asks whether readers leave having learned enough to reach their goal or feel they need to search again. It also says Google has no preferred word count.

So readability affects SEO the way clear writing does, through the people reading. A visitor who gets the answer in one pass has no reason to go back to the results. If an SEO plugin gives you a green light for scoring above 60, that threshold is the plugin's rule, not Google's.

AI answers raise a different question. An answer engine lifts a passage out of your page, so what matters is whether a sentence names its subject and still makes sense alone. Our citability analyzer reviews each section for a clear answer, context and evidence, and the guide to getting cited by ChatGPT covers how ChatGPT search picks what it quotes.

What Flesch reading ease score should you aim for?

Aim for 60 to 70 on pages written for the general public, and stop treating the score as a target on pages written for specialists.

The 60 to 70 band, about grade 8 or 9, fits home pages, pricing pages, product descriptions, help articles and local service pages, and anything a non-expert reads on a phone. If one of those pages scores under 50, look for abstract nouns before you split sentences, because long words cost far more than long sentences. Going far past 80 rarely pays on a sales page. "We make it easy. You will love it." scores 107.6 and gives a buyer nothing to check.

For developer docs, API references, engineering blogs and clinical or legal writing for professionals, 60 is the wrong goal. The vocabulary of those fields is long by nature. Configuration, authentication and replication have five, five and four syllables, and a good Kubernetes guide has to use them. Chasing the score there pushes writers toward vaguer words, which costs the reader more than a long word does.

On those pages, watch sentence length instead. Keep most sentences under 25 words, split any over 40, define each term the first time it appears, and use the same term every time after that.

Check your readability score on a live page

Our readability analyzer scores a public URL or up to 20,000 characters of pasted text. On a URL it reads the main content and skips navigation, header, footer, headings, code, tables and figures, so the score covers the prose a visitor reads. It does not run JavaScript, so paste any copy that loads client-side.

It returns Flesch reading ease with its label, the Flesch-Kincaid grade level, the Gunning Fog index and the counts behind them, including hard words of three or more syllables. It flags sentences of 25 to 39 words as long and 40 or more as very long, warns when reading ease falls below 30, and lists up to 10 rewrite targets, the longest sentences and those with three or more hard words, each with its reason. It withholds the scores for copy that is not in English. It does not rewrite anything for you. Each run costs 5 credits.