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How to Check Your Average Sentence Length (And Why It Matters)

A good average sentence length depends on what you're writing. Here is how to check yours, what range to aim for, and why "just split everything short" is bad advice.

Why Sentence Length Actually Matters

Most writing advice tells you to "keep sentences short." That's incomplete advice. Readers don't get tired from long sentences alone — they get tired from monotonous sentences, whether that monotony is all short and choppy or all long and dense.

What actually predicts how easy a piece of text is to read is your average sentence length combined with how much that length varies from sentence to sentence. A blog post where every sentence runs 8-10 words reads like a children's book. A blog post where every sentence runs 30+ words reads like a legal contract. The sweet spot most readable writing lands in is a mix — some short sentences for punch, some longer ones for detail — averaging somewhere around 15-20 words.

You can't judge this by eye reliably. You need a number.

How to Check Your Average Sentence Length

  1. Open the Sentence Counter tool.
  2. Paste in a full paragraph or article — not just one sentence. Averages only mean something across a real sample of text.
  3. Read the Avg Words / Sentence stat in the right-hand panel.
  4. Check the Sentence Length Mix bar underneath it — this shows how many of your sentences are Short (≤10 words), Medium (11-20), Long (21-30), or Very Long (31+), so you can see variety, not just an average that might be hiding a mix of extremes.
  5. Open the Sentence Breakdown list and sort by Longest first to jump straight to the specific sentences dragging your average up.

Unlike a simple word counter that splits text on every period, this tool recognizes abbreviations, decimal numbers, and initials — so a paragraph full of "Dr.", "U.S.", or "3.5" figures doesn't get miscounted as dozens of tiny fragments, which would throw the average off.

What Counts as a "Good" Average Sentence Length

There's no single correct number — it depends on what you're writing:

Content TypeTypical Avg Sentence LengthWhy
Social media captions8-14 wordsRead on a small screen, often skimmed in seconds
Blog posts and web copy14-20 wordsBalances scannability with enough detail to be useful
Marketing and ad copy6-12 wordsShort, punchy, built for a fast decision
Academic and technical writing20-28 wordsComplex ideas need room, but 30+ starts losing readers
Legal and formal documents25-35+ wordsPrecision is prioritized over readability

If your average is far outside the range for what you're writing, that's a signal — not a rule. A 35-word average in a blog post usually means several genuinely long sentences worth splitting; check the Sentence Breakdown list to find them.

The Sentence Length Trap: Why "Just Split Everything" Is Bad Advice

The most common mistake after checking sentence length is overcorrecting — chopping every long sentence into two or three short ones until the average drops. This backfires. Text made entirely of short, similar-length sentences reads flat and repetitive, which is its own readability problem (this is exactly what the Sentence Length Mix distribution catches that a plain average can't).

The better fix: leave your shortest and punchiest sentences alone, and look specifically at your Very Long (31+ words) sentences using the sorted breakdown. Those are the ones actually costing you readers — usually because they're stacking two or three separate ideas with commas and "and" instead of splitting into separate sentences.

Real Scenarios Where This Comes Up

Publishing a blog post — most readability plugins (like the one in Yoast or Google Docs' analysis) flag "sentences that are too long" without telling you how many or which ones. Paste the draft into the Sentence Counter first to see the full picture before you publish.

Editing a client's copy — freelance editors and content writers often need a quick, objective number to justify a suggested revision, instead of just saying "this feels dense."

Checking an academic draft — a thesis or research paper with an average sentence length above 30 words is a common feedback point from advisors; catching it yourself before submission saves a revision round.

Writing for a global audience — content translated or read by non-native English speakers benefits from shorter average sentence length; checking the number before translation avoids compounding the problem.

SEO content briefs — some style guides specify a target average sentence length as part of on-page SEO requirements. This tool gives you the exact figure to hit.

Common Mistakes

  • Judging length by eye — a sentence with three short clauses joined by commas looks short but counts as one long sentence. Always check the actual word count, not the visual line length.
  • Averaging too small a sample — checking a single sentence or a two-line excerpt doesn't tell you anything about your overall style. Paste in at least a few paragraphs.
  • Ignoring the distribution in favor of the average — a 17-word average could mean every sentence is close to 17 words (fine), or it could mean half your sentences are 5 words and half are 30 (a real problem). Always check the Sentence Length Mix bar, not just the average number.

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