Sentence Length Analyzer
Measure sentence length across a text, see the distribution and variation that create readable rhythm, and find the sentences long enough that a reader loses the thread.
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Variation matters more than average
A text where every sentence runs to eighteen words is exhausting to read even though eighteen is a comfortable length. Prose rhythm comes from variation: a long sentence developing an idea, followed by a short one landing it. Gary Provost's well known demonstration of this makes the point better than any statistic, and it is why average sentence length alone is a poor guide. A standard deviation close to zero indicates monotony regardless of what the mean is.
Where comprehension actually falls
Research on readability consistently finds comprehension declining as sentences pass about twenty five words, and falling sharply beyond forty. That is not because long sentences are wrong but because working memory has to hold the structure open until the sentence resolves. A forty word sentence with three subordinate clauses asks the reader to keep several things suspended at once, and by the end many have lost the beginning.
The fix is usually a full stop
Most over long sentences contain two or three complete thoughts joined by commas, semicolons or the word "and". Splitting them at those joints requires no rewriting: the clauses are already there. The exception is a sentence long because of nested qualification rather than joined clauses, which needs the qualifications moved out or removed rather than a full stop inserted.
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Frequently Asked Questions
What is a good average sentence length?
Between 15 and 20 words for general prose, lower for instructions and technical documentation. What matters more is the variation around that average, because uniform sentence length is tiring to read whatever the mean.
How long is too long?
Comprehension starts declining past about 25 words and falls sharply beyond 40. A long sentence is not automatically wrong, but it should be a deliberate choice rather than an accident of drafting.
Why does variation matter?
Because rhythm comes from contrast. A sequence of similar length sentences reads as monotone even when each is well formed. The standard deviation reported here is a direct measure of that variation.
How should I split a long sentence?
At the joints it already has. Most over long sentences are two or three complete thoughts joined by commas, semicolons or "and", and the clauses are already there to be separated. A sentence long from nested qualification needs the qualifications moved rather than a full stop added.
Does this replace a readability score?
No, it measures one input to readability. Flesch-Kincaid and similar formulas combine sentence length with syllable count, so a text of short sentences full of long words still scores as difficult. This isolates the sentence length half.
Privacy & Security
Everything runs in your browser; nothing is uploaded.
How to Use
Paste your text to see sentence length distribution and which sentences need breaking up.
Disclaimer: This tool is provided "as is" without warranty of any kind. Results are for educational and utility purposes.
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