Sentence Counter
Count sentences in any text and see their average length, longest run, shortest run, and readability impact in your browser.
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Statistics
Sentence stats
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Readability impact
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Download a per-sentence breakdown for editing notes.
What is a sentence counter?
A sentence counter is a small tool that scans your text and tells you how many distinct sentences it contains. It looks for the punctuation that ends a sentence (period, question mark, exclamation mark) and the whitespace or line break that follows, then totals the runs in between. On top of the raw count, this tool also reports per-sentence stats: the average number of words per sentence, the shortest and longest sentence with a preview, and the spread between them. See also: paragraph length.
Why bother? Sentence count is the cleanest single signal for prose rhythm. A draft of 400 words spread across 8 sentences reads very differently from the same 400 words split into 30. The first feels dense and academic. The second feels punchy. Knowing the number lets you decide on purpose instead of by accident.
How sentence length affects readability
Sentence length drives reader effort more than vocabulary does. When a sentence runs long, the reader has to hold more clauses in working memory before they reach the period. Past about 25 words, comprehension drops. Past 40, most readers slow down, skim, or back up to re-read. Below 8 words, the prose can feel choppy and undercaffeinated.
Target ranges differ by format and audience. Technical and procedural writing (manuals, software docs, regulatory copy) reads best at 15 to 18 words per sentence. Academic prose runs longer, typically 18 to 25, because nested clauses are part of the convention. Journalism sits at 12 to 20: short enough to scan on a phone, long enough to carry an idea. Social and product copy lands lower, 8 to 15, because attention budgets are short and most reads happen on small screens.
One number alone (average length) hides a lot. A piece can hit a healthy 17-word average and still feel flat if every sentence is exactly 17 words. That is where variability comes in. A standard deviation of 4 to 8 words gives the prose breathing room: short punches between longer, more developed sentences. Read your own draft and check both numbers together. For longer assignments where the word budget itself is the constraint, pair this page with the Essay Word Counter.
How to use the sentence counter
1. Paste or type your text
Drop a draft, paragraph, chapter, or full document into the text box. Plain text, copy from Word or Google Docs, or text from email and Slack all work. The counter starts the moment you type.
2. Read the live stats
Sentence count is the headline number. Below it, you also get word count, character count, paragraph count, and line count, all updating on every keystroke.
3. Check the sentence-level breakdown
The Sentence stats card shows the average length in words, the shortest sentence (with a preview), the longest sentence (also with a preview), and variability. Use the longest-sentence preview to spot run-ons. Use variability to check rhythm.
4. Apply the readability tip
If your average climbs above 25 words, the tip suggests shorten your sentences. If they're too clipped, see expanding your content. Export the per-sentence report as CSV or TXT to mark up edits.
Sentence counter vs word counter vs paragraph counter
The three tools answer different questions. A word counter tells you how long a piece is in total words, which is the unit most assignments and platforms use as the brief (a 500-word essay, a 280-character tweet, a 1500-word article). It reports words first, with sentences and characters as secondary metrics.
A sentence counter zooms in on prose rhythm. Total word count tells you size; sentence count plus average length and variability tell you how the text reads. Two pieces with the same word count can have very different sentence profiles, and the difference shows up in how a reader experiences them.
A paragraph counter (coming soon) sits above sentence count: it groups sentences into thematic blocks and reports paragraph length distribution. For prose, paragraphs are the unit of argument structure. If you need character-level precision (Twitter/X, meta descriptions, SMS), use the Character Counter instead. For full-length drafts with a target word budget, see the Essay Word Counter, and to browse the full family open all counters.
About wordcounter.ai
Wordcounter.ai is a set of free, browser-based tools for writers, students, editors, and developers. Each tool runs locally, so your text stays on your device. We build the counters we wanted ourselves: fast, focused, and free of pop-ups, sign-ups, or upsells.
Frequently asked questions
What counts as a sentence?
Our counter treats a sentence as any run of words that ends in a period, question mark, or exclamation mark followed by whitespace or end of text. Multiple punctuation marks in a row (?! or …) count as one sentence ending. Quoted dialogue with internal periods is counted as one sentence unless a hard line break follows.
Does the counter handle abbreviations?
Yes. Common abbreviations are recognized and skipped so they do not inflate the sentence count. The list includes Dr., Mr., Mrs., Ms., Jr., Sr., St., Prof., vs., etc., i.e., e.g. and a few academic ones (p., pp., ed., eds., vol., no., fig., al.). Numbered lists like 1. or 2. at the start of a line are also skipped. If you see a count that looks too high, paste a small chunk and check which "period" is being counted; that usually pinpoints the edge case.
What's a good average sentence length?
It depends on audience and format. Plain-language writing for general audiences aims for 15 to 22 words per sentence. Academic prose runs 18 to 25. News writing sits at 12 to 20. Social copy and product UI run shorter at 8 to 15. If your average climbs above 25, readers slow down and skim more. If it drops below 10 across a long piece, the prose can feel staccato and undercaffeinated.
Why is variability useful?
Variability is the standard deviation of sentence length across your text. Low variability (under 4) means every sentence is about the same length, and the prose can feel mechanical. Moderate variability (4 to 8) gives readable rhythm. High variability (over 8) is fine for narrative writing but can confuse readers in technical documents. Aim for moderate variability when in doubt.
How do I count sentences in Microsoft Word?
Microsoft Word does not show sentence count by default. The Word Count dialog (Review › Word Count) reports words, characters, paragraphs, and lines, but it skips sentences. For sentence count, paste the text into this tool. Numbers update as you type, and nothing leaves your browser. Google Docs has the same gap (Tools › Word Count), so the same workflow applies there.
I'm checking sentence count on grant applications and confidential business proposals. Could a reviewer or outside party see my draft?
No. The sentence split runs in JavaScript inside your browser. Grant applications, proposals, and any other confidential drafts stay on your machine. We have no submission endpoint that touches your text.
What's the difference between a sentence counter and a word counter?
A word counter totals individual words. A sentence counter totals discrete sentences and adds per-sentence stats: average length, longest run, shortest run, and variability. For a deeper word breakdown plus sentences and characters in one view, use our main word counter.
Can the counter detect run-on sentences?
The longest-sentence preview surfaces any single run that exceeds 40 words, which is the rough threshold for a run-on candidate in general prose. If the longest sentence sits above that mark, review it for missed periods, comma splices, or a chain of clauses that would read better as two sentences. The tool flags the candidate; the editorial call is yours.
What is a good average sentence length?
15 to 18 words is the sweet spot for general-purpose prose. News writing aims for 15 to 17, blog posts 12 to 18, academic writing 20 to 30. If your average is under 10, the writing reads choppy. If your average is over 25, readers slow down or skim. The table above maps ranges to typical contexts.
Why is sentence-length variability useful?
Sentences of identical length feel monotonous regardless of how good the writing is. Mixing short (5 to 10 words), medium (12 to 18), and long (20+) keeps the rhythm interesting. A passage with all 15-word sentences sounds robotic; a passage that alternates a 6-word punch with a 22-word build-up reads like prose. The counter does not score variability directly but the per-paragraph breakdown lets you eyeball it.
What is the difference between a sentence counter and a word counter?
A word counter reports the total words in your text - the default unit for most writing assignments and word limits. A sentence counter reports the number of sentences plus the average words-per-sentence. Word count answers "how long is my text?". Sentence count answers "how dense is my text?". They are complementary; this page shows both side by side.
Is the text I paste here private?
Yes. The counter is a JavaScript widget that runs in your browser. The text you paste is processed locally and never sent to a server. There is no logging, no upload step, and no account or signup required. You can verify this by opening the browser network tab and pasting text - you will see zero network requests.