The Flesch Reading Ease scale runs from 0 (practically unreadable) to 100 (easy to read).
A score of 60 is taken to be plain English: about 20 words per sentence and 1.5 syllables per word. The Reader's Digest scores 65, Time Magazine 52, the Harvard Law Review 32. In 1991 the state of Indiana legislated a minimum Flesch Reading Ease Score of 40 for insurance policies. Today most US states require insurance documents to score between 40 and 50.
Hope that helps,