WordToolboxAverage sentence length is words divided by sentences. It is the single most useful structural number in an edit, because it correlates with how much effort a reader spends on syntax rather than substance.
Sentence length by content type
| Content type | Average words per sentence | Longest sentence to allow |
|---|---|---|
| Display and search ads | 6–12 | 18 |
| Landing page copy | 8–14 | 22 |
| Email marketing | 10–16 | 25 |
| Blog and magazine articles | 14–20 | 35 |
| News reporting | 15–20 | 30 |
| Product documentation | 15–22 | 30 |
| White papers and reports | 18–24 | 40 |
| Academic writing | 20–28 | 45 |
| Spoken scripts | 10–16 | 22 |
Paragraph length
| Context | Sentences per paragraph | Words per paragraph |
|---|---|---|
| Mobile web | 1–3 | 25–60 |
| Desktop web | 2–4 | 40–90 |
| Print and PDF reports | 3–6 | 70–150 |
| Academic prose | 4–8 | 120–250 |
How to use these numbers
- Paste a section into the counter and read “Avg words / sentence”.
- Compare with the band for your content type.
- Above the band: split the longest sentences at their conjunctions.
- Below the band: join choppy pairs so the reasoning connects.
- Recheck after editing — improvements should show as a shift of several words, not a fraction.
Averages hide variation, and variation is what makes prose readable. A section averaging 17 words should contain sentences of 7 and 30, not twelve of exactly 17.