What is a good average sentence length?

In a hurry? Want the short answer? Scroll straight to the bottom.

As a bit of a science kid in middle school, I tended to stay away from writing as much as I could. When the time came for an essay, I really had to concentrate the full force of my illiterate mind on getting it done. Come hand-in time, I would usually produce something that I was quite proud of, and that got decent marks, but, the same critique always seemed to pop up: “Joseph, you’re keeping the reader on their toes for too long. You need to give them rests.” She was of course referring to my criminal sentence lengths.

Two main reasons should affect you into optimising your sentence length: The first is for achieving a smooth rhythm, and the second is to cultivate ease of understanding.

Rhythm is one of the most important qualities of a writer. It’s something that can take a long time to perfect and that can make a few simple sentences become animated in the minds of the reader. The central factor that creates rhythm is the length of your sentences. We’re not talking about the average sentence length here, we’re actually talking about the variation of the sentence length. If you vary your sentence lengths, you create the potential for rhythm. And now that you’ve got the potential, you just need to optimise and re-optimise until you find it.

The second result of efficiently and effectively choosing how many words a sentence should have, is increased understanding. Lengthy sentences can be really hard to understand because without pausing, the reader has to keep track of everything that you’re saying and link it with everything that you’ve said to try to maintain some context, but when the reader reaches about this point here, they start to feel that the information they’re trying to take in is a little bit harder to process because they’re not given any time to absorb each point that the writer makes, they don’t get time to ‘feel’ each chunk of information as it comes. The previous sentence tries to illustrate this concept (just in case you didn’t catch that). If your sentences are too short, you risk sounding like a 2nd grader and your writings may seem to be choppy and without flow.

In order to avoid marathon, comma plagued sentences, and tiny, childlike sentences we can look to the following tips for some guidance:

  • Keep your sentences short, but not overly so. In the Oxford Guide To Plain English, Martin Cutts suggests: “Over the whole document, make the average sentence length 15-20 words.”
  • Keep an eye on your rhythm. Sometimes a longer sentence is best, sometimes a shorter.
  • Avoid using uniform sentence lengths.
  • Your average word length can affect your ideal sentence length. Don’t try to fill your sentences with abstruse language, and the 15-20 words rule will hold.


Conclusion: How many words should a well-written sentence have?

As you might expect, there is no perfect. Try to stick to 15-20 words on average, big words will decrease this number, make sure to vary the length of your sentences.

Want to know the some info about your prose? You can calculate all sorts of statistics (including sentence length) by using Count Wordsworth. It’s a neat little tool that’s the best at what it does on the net.

February 18, 2013