In this article
Why does one article feel effortless and another feel like wading through mud, even when both are about the same thing? Much of it comes down to two numbers: how long your sentences are, and how long your words are. The Flesch reading ease score turns those two numbers into one.
The formula in plain words
The score was devised by Rudolf Flesch in 1948. It has two levers. The first is the average number of words in a sentence. The second is the average number of syllables in a word. More of either lowers the score.
What the number means
The marker is the example sentence below. Bands follow the standard published table.
Two sentences, scored by hand
Check them: 206.835 − 1.015 × 16 − 84.6 × (21 ÷ 16) = 79.6. The score can go above 100 for very short sentences.
Which lever should you pull?
Sentence length usually moves the score fastest, because splitting one long sentence in two cuts the average without changing a single word. Word length helps more slowly: “use” instead of “utilise” saves a syllable each time.
Aim for a mix. Vary the length, but keep most sentences short.
What the score cannot tell you
- Whether it is true or useful. Nonsense in short words scores very well.
- Whether it is well organised. Headings, order and examples matter just as much.
- Technical words that are easy for your audience. “Algorithm” is long, but fine for programmers.
- Languages other than English. The constants are tuned for English syllables.
Five quick edits that raise the score
- Cut every sentence over 25 words in two.
- Swap a long word for a short one when the meaning is the same.
- Use the active voice. “We moved the meeting” beats “The meeting was moved by us.”
- Delete filler openings like “It should be noted that”.
- Read it aloud. If you run out of breath, the sentence is too long.
Word and character limits are a different constraint. For those, see how long is long enough.
Questions people ask
What is a good Flesch reading ease score?
60 to 70 is usually called plain English, and most writing for the general public aims for 60 or above. Technical or legal writing is often 30 to 50.
How is the Flesch reading ease score calculated?
206.835 minus 1.015 times the average words per sentence, minus 84.6 times the average syllables per word.
Can the score be above 100 or below 0?
Yes. Very short sentences of one-syllable words can score above 100, and very long sentences with long words can score below 0.
Does a high score mean good writing?
No. It only measures sentence and word length. A text can score high and still be confusing, inaccurate or badly organised.
How do I improve my readability score?
Shorten your sentences first, then replace long words with shorter ones. Using the active voice and cutting filler phrases both help.