The Flesch Reading Ease score, developed by Rudolf Flesch in the 1940s, rates English text on a scale where higher numbers mean easier reading. It uses only two inputs: average words per sentence and average syllables per word. Its companion, the Flesch-Kincaid Grade Level, converts the same inputs into an approximate US school grade. Many writing tools and SEO plugins report one or both.
The formulas
Both formulas reward shorter sentences and shorter words. Scores in the 60s and 70s are generally described as plain English; scores below 30 are typically academic or legal text.
Reading Ease = 206.835 - 1.015 x (words / sentences)
- 84.6 x (syllables / words)
Grade Level = 0.39 x (words / sentences)
+ 11.8 x (syllables / words) - 15.59What it misses
The formula cannot tell whether text is accurate, well organized or meaningful. It penalizes long technical words that your audience may know well, such as "authentication" or "infrastructure," and it ignores headings, lists and layout. Two pages with identical scores can differ hugely in how easy they are to use.
Google has not indicated that it uses Flesch scores in ranking.
How to use it
Use the score as a flag. If a page scores far lower than similar pages on your site, look for long sentences and needless jargon. Do not rewrite technical content to hit a number if it means losing precision.
Example
Spotting the outlier
Hypothetical compliance tool Hearthpost scored all its blog posts. Most sat in a similar band, but its GDPR guide scored far lower. The cause was a handful of paragraphs copied from legal text. Rewriting those in plain language and quoting the regulation only where the exact wording mattered fixed the outlier.
Common mistakes
Chopping sentences to raise the score
Fragmented writing can score well and still read badly. Edit for clarity, then check the score, not the reverse.
Questions
It depends on audience. General consumer content often aims higher than technical B2B content. Compare against similar pages rather than a universal target.
