Reading Level Checker

A passage can use short sentences and familiar words yet still be hard to follow because it assumes background knowledge, hides the main point, or uses poor layout. Reading-level formulas measure narrower surface features. They estimate how much schooling a reader may need for the sentence length and word complexity in a sample, not whether a particular audience will understand, trust, or act on it.

Different formulas look at different clues. Flesch-Kincaid and Flesch Reading Ease use words per sentence and estimated syllables per word. Gunning Fog and SMOG emphasize words with three or more syllables. Coleman-Liau and the Automated Readability Index use letter counts instead of syllables. The same passage can therefore receive several defensible but noticeably different scores.

• Long sentences raise several grade estimates because they increase the average number of words per sentence.
• Longer or multisyllabic words raise formulas that treat word length as a sign of vocabulary difficulty.
• Sentence splitting changes the denominator, so bullet lists and text with sparse punctuation need special care.
• Sample length affects stability. A slogan or short notice can swing sharply when one word or punctuation mark changes.

A target grade band is best used as a comparison range, not a command to remove every long word. Necessary terms can stay when they are defined near a concrete example. Chopping accurate ideas into tiny sentences may lower a score while making the passage less coherent. Revision should preserve meaning first, then improve wording, sequence, examples, headings, and layout.

These formulas are intended for English prose. Their syllable, abbreviation, and sentence rules do not transfer cleanly to other languages, mixed scripts, code, tables, poetry, or highly fragmented text. Human review with representative readers remains the strongest check on real comprehension.

How to Use This Tool:

Analyze one coherent English passage at a time so the formula scores and revision cues refer to the same audience and purpose.

1. Paste the passage or load one plain TXT file of 2 MiB or less. Use a longer sample when possible; fewer than 30 words produces a strong short-sample warning and fewer than 100 words produces a limited-sample warning.
2. Select the intended Target grade band or choose no target, then keep Consensus median for a balanced headline or select the named formula required by your review process. For bullets or notices with little punctuation, switch Sentence splitting to Line-aware.
3. Review the Formula ledger for score disagreement and the Revision queue for sentences and words that meet the current thresholds. Keep necessary terms and fix meaning, definitions, and organization before chasing a lower number.

Interpreting Results:

The headline grade is either the selected formula or the median of five grade formulas. Within target means that unrounded grade falls inside the selected inclusive range. Below target and Above target are comparison labels, not quality judgments.

The formula spread is the highest grade estimate minus the lowest. A wide spread signals that sentence length, syllables, complex-word share, and character counts are telling different stories. Read the individual rows before deciding what to revise.

Flesch Reading Ease runs in the opposite direction from grade level: higher values indicate easier surface reading. The revision queue is separate from every formula. Changing the long-word or long-sentence threshold changes which items are flagged, but it does not change the readability scores.

Technical Details:

All formulas share one tokenized passage but weight its counts differently. The analysis counts Unicode word tokens, sentences, letters, estimated syllables, and complex words. A complex word has at least three estimated syllables. Each grade estimate is limited to the range 0 to 18 before the consensus median and spread are calculated.

Formula Core:

The following equations use the unrounded counts. Displayed grade values are formatted to one decimal place, while later calculations retain the full internal result.

The consensus grade is the median of the five clamped grade estimates. With five values, the third score after numeric sorting becomes the median. The formula spread is the maximum grade minus the minimum grade. Target fit uses the unrounded headline grade: below the lower bound is Below target, above the upper bound is Above target, and both endpoints belong to Within target.

Transformation Core:

Standard splitting recognizes sentence-ending punctuation while protecting a small set of common abbreviations. Punctuation-only mode removes that abbreviation guard. Line-aware mode treats non-empty lines as sentence-like units when punctuation does not separate them. This choice can materially change words per sentence and every formula that uses it.

Syllables are estimated with an English vowel-group heuristic after case folding, accent removal, and removal of nonletters. Words of three letters or fewer count as one syllable. A trailing e, es, or ed is removed before vowel groups are counted, and certain final vowel pairs receive one extra syllable. The minimum is one syllable per token. This transparent approximation will miscount some names, abbreviations, loanwords, and irregular English words.

Accuracy and Privacy Notes:

Passage text and TXT files are analyzed in the browser and are excluded from the page URL. A source label is optional and does not change the scores. The formulas estimate surface difficulty only; they do not measure comprehension, prior knowledge, accuracy, motivation, translation quality, visual design, or accessibility.

Worked Examples:

References:

• Derivation of New Readability Formulas for Navy Enlisted Personnel, Kincaid, Fishburne, Rogers, and Chissom, 1975.
• Get to the Point: Write for Immediate Understanding, Centers for Disease Control and Prevention.
• SMOG Readability Formula, Harvard T.H. Chan School of Public Health.