Flesch Reading Ease
A 0–100 score where higher means easier to read. 60–70 is plain English.
Flesch Reading Ease (FRE) is a readability formula published by Rudolf Flesch in 1948. It returns a score from roughly 0 to 100, where 100 is a children's book and 0 is an academic paper. The formula uses only two inputs: average sentence length and average syllables per word. It doesn't understand meaning, but it reliably correlates with human difficulty ratings. A score of 60 is considered plain English readable by an 8th–9th grader. News articles typically land at 55–65. Legal and academic writing sit below 30.