Roughly 90 episodes are considered filler. Notably, the series finishes its main manga-based story at episode 135, followed by a massive block of filler until the final episode (220).
To understand the number, you need to know the two distinct parts of the story.
Watching the entire 720-episode saga is a significant time commitment. With each episode averaging about 23 minutes (including intros and outros), the math breaks down as follows:
Teenage Naruto's quest to save Sasuke and the Fourth Great Ninja War. 720 Understanding "Filler" vs. "Canon"
Approximately 203 episodes are filler, meaning nearly 40% of the series consists of non-manga content. How Long Does it Take to Watch?