I just compiled this to get a perspective of how many fillers are there in each Anime.
Onepiece (Individual Filler episodes included) (Ongoing Anime)
Total Episodes - 395
Total fillers - 73 (including specials and recap episodes)
Total non-filler episodes - 321
Filler/non-filler ratio - 1 : 4.4
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Bleach (Individual Filler episodes included) (Ongoing Anime)
Total Episodes - 214
Total fillers - 87
Total non-filler episodes - 126
Filler/non-filler ratio - 1 : 1.48
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Naruto (Individual Filler episodes before Episode 130 not included) (Completed Anime)
Total Episodes - 220
Total fillers - 85
Total non-filler episodes - 135
Filler/non-filler ratio - 1 : 1.59
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16/80 Naruto Shippuuden (Individual Filler episodes included) (Ongoing Anime)
Total Episodes - 80
Total fillers - 16
Total non-filler episodes - 64
Filler/non-filler ratio - 1 : 4
For every filler episode there are 'the above highlighted number' of main story(or canon) episodes.
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What is a filler?
Usually fillers are episodes which are not part of the original story of the manga. Anime like Onepiece, Bleach & Naruto are taken from the manga(Comics is called Manga in Japan). Usually manga is ahead of the Anime. When the manga is made, the Anime is made by taking the story from the manga. Usually the Manga is ahead of the Anime by 20 or so episodes. But at times the manga is not released regularly because the original story creator cannot think of any worthwhile story. So when this happens the Anime quickly catches up with the Manga and the 20 Episode buffer between the 2 becomes less than 10 episodes. To maintain the 20 episode buffer, the Anime introduces additional stories which are not part of the Manga. It's nothing but lame ass stories to pass the time. Filler stories/episodes have a weak story and are generally very poorly written by people who are not the original creator. The plot never progresses in the Filler stories. It's just for time pass.
I just mentioned 20 episodes as an example. It may be 20, 30 or even 40 episodes. The reason why there is a buffer is because if the Anime catches up with the Manga then everyone will start watching the Anime and not read the Manga since both are releasing at the same time. By maintaining a time/episode difference, usually several months, people who are anxious will go and buy the manga instead of waiting for months to see the Anime. So it's double the profit.. profit for both the Anime & the Manga.
I mentioned fillers are crappy stories, but it's not always that case. Sometimes fillers are extremely well done. Quite a few of the Onepiece and Naruto(fillers before episode 130) fillers are quite good. And I absolutely love Getbackers fillers, especially the Hospital filler. The fillers in Bleach are THE worst of the worst. You can't get any filler worse than bleach's fillers. But even bleach's fillers are better than some of the wholesome Anime & Manga out there. So there you have it.
If there are filler list & ratios from any other anime then share it here.
