The best sentences are around 15-18 words long. Some sentences will be longer, but try keep your sentences to no more than 21-24 words at the most. This helps you keep your sentences grammatical because longer sentences need more conjunctions and more punctuation. Shorter sentences are easier for your reader as well.
When you find a sentence that is longer, for example 30 words or more, you should check that particular sentence very carefully because longer sentences are more likely to have errors with clause structure and conjunctions.
Use the Find function in Word to find all periods (full-stop punctuation) in your text. The yellow highlighting of all the periods will show which sentences are longer. Check the number of words in these sentences by selecting the whole sentence as if you were going to copy it, and the check the statistics at the bottom of your screen in Word.
Rules for Long Sentences
1. Linking words (e.g., however, which, even though, etc.) should go between clauses.
2. Some sentences are long because they contain lists. Review APA guidelines on lists to ensure your punctuation is correct.
3. Use as few commas as possible and avoid semicolons and parentheses (rule for long sentences only). If your sentence has multiple punctuation marks, use a period where appropriate.
4. Avoid adding extra information at the end of a sentence if the sentence is already 15-20 words long.
Wallwork, A. (2011). English for writing research papers. Springer. https:doi.org/10.1007/978-1-4419-7922-3