Sentence Counter & Readability Analyzer

Sentence count is the one metric almost every writing tool omits. Word processors show word count in the status bar; readability checkers give you a grade level; nothing simply tells you how many sentences you wrote, how long they run on average, or which one is carrying the most weight. Advanced Sentence Analyzer fills that gap with a full breakdown that updates the moment you stop typing.

Writers and editors use average sentence length as a proxy for rhythm. Academic style guides cap it at around 20 words. Plain-language standards for government documents target 15. Marketing copy often sits below 10. Knowing where your draft lands, and which specific sentence is dragging the average up. That is more useful than a single readability score that tells you nothing about where to edit.

Worked Example: The Gettysburg Opening

Click Load Sample to paste the opening paragraph of the Gettysburg Address. The analyser splits it into 4 sentences and reports an average of around 33 words per sentence, well above most plain-language targets. The Flesch score lands near 40, labelled Difficult, which matches the formal 19th-century register. All four sentences fall into the Long (>25 words) bucket, so the complexity bar is entirely red.

• The Longest sentence card quotes the sentence verbatim with a word count beside it, and a Copy button lets you paste it straight into a rewrite or a comment.
• The expandable View all sentences panel lists every sentence numbered, with its word count colour-coded green (short), yellow (medium) or red (long). This is the fastest way to find the one sentence that is pulling up the average.
• Abbreviations like Mr., Dr., vs. and month names are not treated as sentence-ending periods, so Dr. Chen arrived at 9 a.m. on Monday. counts as one sentence rather than three.

The Formula Behind the Flesch Score

The Flesch Reading Ease formula is 206.835 − 1.015 × (words / sentences) − 84.6 × (syllables / words). A higher score means easier reading.

• Scores 90–100 are rated Very Easy: comics, basic instructions.
• Scores 60–70 are rated Standard: newspaper prose, most web copy.
• Scores below 30 are rated Very Confusing: dense legal or academic text.
• Syllable counting uses a vowel-cluster heuristic. The word sequences gets three syllables, civil gets two. Proper nouns and uncommon words may be off by one, which moves the Flesch score by a fraction of a point at typical text lengths.

Tricky Inputs: Ellipses, Bullets and No Terminal Punctuation

• A fragment with no terminal punctuation (a heading, a label, a list item) produces the message No sentences detected — try adding a period, question mark, or exclamation point. It is not counted as a sentence because the splitter requires at least one terminator to avoid splitting mid-abbreviation.
• Inputs over 50,000 characters are blocked before analysis begins: Input exceeds 50,000-character limit. A character counter in the top-right corner of the input field tracks how close you are.
• Multiple exclamation or question marks (!!!, ???) collapse into a single sentence boundary, so a three-exclamation-mark ending adds one sentence, not three.
• The sentence list panel is collapsed by default and opens on demand, so a 200-sentence paste does not flood the page before you have read the summary cards.