Prepare the input
Paste representative English prose. Remove navigation or code when readers do not treat it as prose, and retain terminology that the audience genuinely needs.
Inspect English sentence and syllable signals
Readability Checker
Estimate Flesch Reading Ease and Flesch-Kincaid grade level from English prose, alongside words, sentences, syllables, and average sentence length. Scores use a syllable heuristic and measure surface structure only; they do not judge accuracy, accessibility, tone, inclusiveness, expertise, or suitability for a specific reader.
- 01Private by designYour text stays in this browser tab.
- 02Bounded and responsiveUp to 250,000 characters for bounded local analysis.
- 03Ready to reuseCopy the result or download a branded TXT file.
Counting and transformations run locally. Nirmion does not send the text in this workspace to an API.
Product guide
Use readability as a diagnostic, not a writing verdict
Formula scores can identify dense sentence and word patterns, but good content still depends on purpose, prior knowledge, vocabulary, structure, and testing. Review the complete result in its destination because automated text rules cannot infer every language, house style, data model, or publishing intention.Choose the rule
The checker reports both Reading Ease and grade level so a single number does not hide the formula basis. No target score is imposed automatically.
Review the output
Compare versions, inspect long sentences and unexplained terms, and test comprehension. Do not simplify legal, medical, safety, or technical meaning merely to move a score.
How it works
Published English formulas with heuristic syllables
Words and likely sentences are counted from Unicode text, while English syllables are estimated from lowercase vowel groups with a simple silent-ending adjustment. Flesch Reading Ease uses words per sentence and syllables per word; Flesch-Kincaid grade level applies its published weighted form. Scores are rounded for display. Input is capped at 250,000 characters, empty or symbol-only prose is rejected, Reading Ease is displayed within 0 to 100, and no remote model is called. The operation runs in this browser tab, applies explicit bounds before expensive work, and does not send workspace text to a Nirmion API.
Useful when
Compare drafts with structural evidence
Use readability metrics to prompt questions about density and audience, not to replace editorial, accessibility, or subject-matter review.
- Compare two versions of public guidance, onboarding, help content, lessons, or policy explanations before user testing.
- Identify unusually long average sentences that deserve a closer manual pass for structure and cognitive load.
- Document the formula result alongside audience research rather than claiming an automated quality or accessibility grade.
Questions answered
Readability Checker questions
Practical boundaries matter with text tools. These answers explain what is measured, what is retained, and when a manual review is still needed.
What does a Flesch score mean?
It estimates structural reading ease from sentence length and syllables. Higher scores are often easier by the formula, but context and audience still govern usefulness.
Can I check another language?
The operation will run, but the syllable heuristic and formulas are English-oriented, so non-English scores are not supported or reliable.
Does this certify accessibility?
No. Accessibility includes structure, semantics, interaction, alternatives, cognition, language, visual presentation, and testing beyond a prose formula.
Privacy and retention
Your draft stays on your device.
Nirmion performs these operations with browser JavaScript. The workspace does not call the catalogue API with your source text, and completed-job content is kept only in this component memory for re-download.
A downloaded file remains in your browser downloads, device storage, backups, and any location where you share it. Clear or close the page when working on a shared device, and avoid pasting secrets into extensions or third-party clipboard managers.
Tool details
Transparent English readability formulas with boundaries
Nirmion Readability Checker calculates Flesch Reading Ease and Flesch-Kincaid grade estimates together with words, likely sentences, estimated syllables, and average sentence length. The combined view helps editors compare English drafts without treating one score as a complete quality judgement. Words and likely sentences are counted from Unicode text, while English syllables are estimated from lowercase vowel groups with a simple silent-ending adjustment. Flesch Reading Ease uses words per sentence and syllables per word; Flesch-Kincaid grade level applies its published weighted form. Scores are rounded for display. This makes the behavior inspectable and repeatable instead of presenting an unexplained result.
The report downloads as text_nirmion_tools_readability_report.txt for text up to 250,000 characters. The method and English-only syllable heuristic are documented, and the page rejects claims of accessibility certification or audience comprehension. The operation runs in this browser tab, applies explicit bounds before expensive work, and does not send workspace text to a Nirmion API. Downloading clears the active workspace while the latest three completed results remain available in this tab for re-download.