Sentence Counter

What the Sentence Counter Does

It gives you a quick statistical read-out of a piece of text: how many sentences and words it contains, how many paragraphs, and crucially the average words per sentence — the single number that matters most for readability.

It is a counting tool, not an editor. It does not rewrite, grade or score your writing; it reports what is there so you can check a length limit or spot sentences that have grown too long.

How It Works

The counts recalculate on every keystroke, with no button to press. Paste or type into the box and the four figures update instantly.

Because it runs in JavaScript on your device, there is no upload step and no waiting — it works the same on a phone as on a laptop, and offline once the page has loaded.

Methodology

1. Detect sentence boundaries. It scans for runs of text that end in a full stop, question mark or exclamation mark, counting each run as one sentence. If you paste text with no ending punctuation at all, the whole block counts as a single sentence.
2. Count words. It trims the text and splits on any run of spaces, tabs or line breaks. Every resulting chunk is one word, so a contraction like don't and an abbreviation like U.S.A. each count as one.
3. Measure paragraphs. It splits wherever a blank line appears — that is, two or more line breaks in a row. A single line break does not start a new paragraph.
4. Compute the average. It divides words by sentences and rounds to one decimal place, giving the average sentence length that plain-language guides care about. All four figures refresh live as you type.

How the counts are derived

Readability guides put the comfortable average at 15 to 20 words per sentence; this figure is what you watch to keep prose readable.

Privacy

Your text is analysed entirely in your browser with JavaScript. Nothing you paste is uploaded, logged or stored on any server.

Because the counting is local, the tool is safe for unpublished drafts, client copy or confidential notes — close the tab and everything is cleared.

Technical Details

Standards & references

• Sentence boundary disambiguation — The classic natural-language problem of deciding where sentences end. A period can mark an abbreviation, a decimal, an ellipsis, an email or a URL, not only a sentence ending.
• Plain-language sentence length — The International Plain Language Association and Martin Cutts's Oxford Guide to Plain English put the readable average at 15 to 20 words per sentence, with single sentences kept under about 35.

Accuracy & Limitations

Sentence detection is punctuation-based, so abbreviations and decimals inflate the count. Dr. Smith paid 3.5 million. reads as three sentences, not one, because each period looks like an ending. In studies of newspaper text, a large share of periods are abbreviations or decimals rather than sentence ends.

An ellipsis (three dots) counts as a sentence ending, and text with no full stop at all is treated as a single sentence.

Words are whitespace-separated, so a hyphenated word, a contraction, or a number like 1,000 each count as one word.

Paragraphs split only on a true blank line. If your text uses a single line break between paragraphs, they are counted as one.

Real-World Use Cases

When to use it — and when not to

For a reading-ease grade use the Readability Checker; for word and character totals with reading time use the Word Counter; for keyword frequency use the Keyword Density Checker.

Frequently Asked Questions

References

• Sentence boundary disambiguation — Wikipedia
• Is Segmentation a Solved Problem? — TM-Town
• Sentence length — Readability Guidelines

Related Tools