Free readability checker

Readability is how easy a piece of text is to read and understand. In practice it is measured with formulas that look at two things: how long your sentences are and how long your words are. Those two inputs predict comprehension surprisingly well, which is why plain-language guidance for government, health and legal writing is built on them. Readability says nothing about whether the ideas are good — only about how much work the reader has to do to get at them.

Every common readability formula combines average sentence length with a measure of word difficulty. Flesch Reading Ease is 206.835 minus 1.015 times words per sentence minus 84.6 times syllables per word. Flesch-Kincaid grade level is 0.39 times words per sentence plus 11.8 times syllables per word minus 15.59. Gunning Fog uses the share of words with three or more syllables instead, and Coleman-Liau and ARI use characters per word so they need no syllable counting at all.

Aim for 60 to 70 for a general audience — that band is defined as plain English and is what most US adults read comfortably. Above 80 is very easy, the level of a tabloid or a children's book. Between 50 and 60 is fairly difficult and suits an informed or trade readership. Below 30 is the territory of academic papers, contracts and insurance policies, where most readers have to reread sentences to follow them.

Grade 8 to 9 for anything aimed at the general public. That is the average adult reading level in the US and UK, and health, government and plain-language standards usually ask for grade 8 or lower. Public health information is often held to grade 6. Technical and trade writing sits higher and that is fine, as long as it matches the people actually reading it. Writing below your audience's level costs nothing; writing above it loses readers.

Flesch-Kincaid grade level converts a text's difficulty into a US school year, so a score of 8 means an average eighth-grader, around thirteen years old, could read it once and follow it. It uses the same two inputs as Flesch Reading Ease — words per sentence and syllables per word — but scales them so the output is a year rather than a 0 to 100 score. It was developed for the US Navy in 1975 to grade training manuals, and it is the figure most style guides and word processors report.

The Gunning Fog index estimates the years of formal education a reader needs to understand a passage on the first reading. It is 0.4 multiplied by the sum of average sentence length and the percentage of complex words, where complex means three or more syllables, excluding proper nouns, familiar compounds and verb endings such as -ed and -es. A Fog score of 8 is easy reading for most people; business writing commonly lands around 11 to 14, and anything above 17 reads as academic.

Cut the long sentences first. Sentence length is the heavier input in every formula, so splitting a 40-word sentence in two moves the score more than any word-swapping. Then replace Latinate words with short ones: utilise becomes use, facilitate becomes help, in order to becomes to. Put the main clause first, use active verbs, and drop the adverbs that are doing no work. Aim for an average of 15 to 20 words per sentence with real variation between them.

Not directly. Google has no readability score in its ranking systems and has said so repeatedly. What readability changes is whether people finish the page, whether they come back, and whether anyone links to it — and those do feed the signals search engines can measure. It matters more now that answer engines quote pages: a short, plainly worded sentence is far easier for a model to lift as a citation than a 45-word one with three subordinate clauses.