American Press Institute correlates sentence length, comprehension
How long should sentences be? A better question might be: How much of your piece do you want your readers to understand?
The longer the sentence, the less readers comprehend, according to a study by the American Press Institute. The research, based on studies of 410 newspapers, correlated the average number of words in a sentence with reader comprehension.
|The fastest way to increase understanding?|
Reduce sentence length
|Average number of words|
|Up to 8||100%|
|9 to 14||> 90%|
|15 to 18||> 80%|
|19 to 21||> 70%|
|22 to 25||> 60%|
|26 to 28||> 50%|
|29 to 32||> 40%|
|33 to 36||> 30%|
|35 to 39||> 20%|
|40 to 42||> 10%|
|43 or more||< 10%|
|Add a word, reduce comprehension Seeking more than 80% understanding? Keep your sentences to less that 19 words, the API study found.|
The study found that:
- With average sentences of 8 words or less, readers understood 100% of the story. (Downside: Copy might sound as if it had been ripped from a Dick and Jane book.)
- At 14 words, they understood 90% of the information.
- At 43 words, they understood less than 10%.
That means that at 46 words, this sentence would generate less than 10% comprehension:
And what about that 147-word sentence the VP wants you to run in tomorrow’s blog post? Readers not only don’t understand what you wrote, but they also forget their Social Security numbers. That’s a net loss of knowledge — not exactly our goal as communicators.
So how long should sentences be?
Keep sentences shorter than 21 words, suggests the API research.
What’s your average sentence length? What sentence length do you aim for?