How Readability Scores Affect Reader Engagement

Readability scores estimate how easy a piece of text is to read, based on things like sentence length and word length. Easier text tends to keep more readers going, but the scores are rough guides, not goals in themselves.

The main formulas

• Flesch Reading Ease (Rudolf Flesch, 1948): a score from about 0 to 100, where higher is easier. Plain English usually lands around 60 to 70.
• Flesch-Kincaid Grade Level (1975, developed for the US Navy): the US school grade needed to understand the text.
• Gunning Fog Index: years of education needed, weighted by long words.
• SMOG: often used for health materials, based on words with three or more syllables.

All of them count sentences, words and syllables. None of them read for meaning.

How readability affects engagement

• Fewer people give up: long sentences and dense words make readers work harder, and online they can leave in a click.
• Faster scanning: short sentences and familiar words are easier to skim.
• Wider reach: easier text works for non-native speakers, tired readers and people with reading difficulties.
• Even experts prefer it: specialists reading in their own field still appreciate plain writing.

The US Plain Writing Act of 2010 requires federal agencies to write public documents clearly for this reason.

What the scores miss

• Structure: headings, lists and paragraph breaks matter but don't change the score.
• Jargon: a short unfamiliar word scores as easy.
• Logic: short sentences can still be confusing if ideas are out of order.
• Audience: technical readers may need precise terms that raise the score.

Using scores well

1. Write for your reader first.
2. Check the score to spot problem areas, such as very long sentences.
3. Rewrite the worst sentences, then read the piece aloud.
4. Don't chop sentences just to improve a number; that can make text choppy.

Check your text

The readability checker runs several formulas on pasted text at once. Word Counter shows words, sentences and reading time for any page or selected text.

Quick fixes that raise readability

• Split sentences over about 25 words.
• Swap long words for common ones: "use" for "utilize," "help" for "facilitate."
• Use active voice: "we fixed the bug" rather than "the bug was fixed by us."
• Define technical terms the first time you use them.

See checking reading level and writing scannable content.