The difficulty level or grade of Beethovens Moonlight Sonata 3rd movement is a topic of debate, but according to some sources, it is considered to be around grade 8 or 10. The Royal Conservatory of Music (RCM) in Toronto ranks the entire sonata, including the 3rd movement, as ARCT level, which is the highest level in their rating system. However, it's important to note that grading systems can vary and that the difficulty of a piece can depend on the individual's skill level and experience.