Readability Score Checker

The formulas measure two things only

Almost every readability formula combines sentence length with word length or syllable count. Flesch Reading Ease returns 0 to 100 where higher is easier; 60 to 70 is described as plain English and most general-audience writing targets it. Flesch-Kincaid Grade Level converts the same inputs into a US school grade. Gunning Fog counts words of three or more syllables. SMOG is calibrated for health materials and is deliberately conservative. They disagree with each other routinely, which is a fair reminder of how crude the underlying measure is.

What they cannot see

A formula cannot tell whether a sentence makes sense. "Colourless green ideas sleep furiously" scores as easy. So does a paragraph of jargon written in short sentences, because the words happen to be short. Conversely, clear writing about a technical subject scores badly purely because the correct terms are long. Optimising the number rather than the writing produces text that is choppier and no clearer — the classic failure mode is chopping one coherent sentence into three fragments to move the score.

Where the targets come from

Public-facing government and health material is commonly required to hit grade 8 or lower, because that is around the median adult reading level in English-speaking countries. Insurance and legal plain-language rules often specify a Flesch score. Journalism targets grade 9 to 11. These are floors for accessibility, not marks of quality: adults who read comfortably at grade 14 still prefer grade 8 prose, because reading is easier and nobody chooses difficulty for its own sake.

Syllable counting is approximate

Every formula depends on counting syllables, and doing that reliably in English requires a pronunciation dictionary. Tools use heuristics based on vowel groups, which mishandle names, acronyms, hyphenation and loanwords. Two tools will give slightly different scores for identical text. Treat a difference of half a grade level as noise.

Use it as a smoke detector

The productive use is spotting outliers. One paragraph scoring five grades above the rest usually contains a sentence that ran away, a stack of nested clauses, or unexplained jargon. Fix that paragraph and the whole document improves. Chasing a target score across every sentence does not work and is not the point.

Structure matters more than the formula measures

Headings, short paragraphs, lists, and putting the conclusion first affect comprehension far more than average sentence length, and no standard formula accounts for any of them. A document can score badly and read well because it is organised, and score well and read terribly because it is not.