Quick answer
For most web and business writing, averaging 15–20 words per sentence reads as clear and easy to follow. Fiction and literary writing can run longer; technical instructions and UI text should usually run shorter, closer to 10–15 words.
Why sentence length drives readability
Readability formulas like Flesch Reading Ease weigh sentence length heavily, alongside word length, because long sentences force a reader to hold more unresolved information in their head before reaching a full stop. A sentence with three clauses, two commas, and a semicolon is harder to parse than the same ideas split into two or three shorter sentences — even if every individual word is simple.
Target ranges by context
- Web and marketing copy: 12–18 words average — short enough to scan on a phone screen.
- Business and professional writing: 15–20 words average — clear without feeling choppy.
- Technical instructions, UI text, warnings: 8–14 words — one instruction per sentence, nothing to misread.
- Fiction and narrative writing: varies deliberately, often 10–25+ words, since rhythm and voice matter more than a formula.
Variety matters more than a fixed number
A text where every sentence is exactly 17 words reads as flat and mechanical, even though the average looks ideal. Good writing mixes short sentences for emphasis with longer ones for detail and flow. Aim for an average in the right range, not uniform sentences.
How to find your long sentences
- Paste your text into the readability score tool to see your Flesch Reading Ease score and grade level.
- Scan for sentences with more than one comma or more than 25–30 words — these are usually the ones worth splitting.
- Split at the natural break: where "and," "but," or a new idea starts is often a good place to begin a new sentence.
A quick before-and-after
Before: "The report, which was compiled over several weeks by three different teams and reviewed by legal before being sent to the board, highlighted a number of concerns that needed to be addressed before the next quarter." (41 words)
After: "Three teams spent several weeks compiling the report. Legal reviewed it before it went to the board. It flagged several concerns that need addressing before next quarter." (27 words across three sentences)
Related reading
For the full readability picture beyond just sentence length, see what counts as a good Flesch Reading Ease score. For word choice more broadly, see how to improve your writing with better word choice.
Frequently asked questions
What is a good average sentence length?
For general web and business writing, 15–20 words per sentence on average reads as clear and easy to follow. Mixing shorter and longer sentences reads better than keeping every sentence the same length.
Is a long sentence always bad?
No. An occasional longer sentence is fine, especially to vary rhythm. The problem is when most sentences are long, or when a long sentence stacks several ideas without clear structure.