What everyone else said, in recent episodes its been like one manga chapter per episode with a lot of filler thrown in, but there are episodes that can cover 3 chapters sometimes
It depends if the chapters are mostly dialogue, or fighting. Dialougue always fills up an anime better, but two, or three chapters of fighting might fill up one anime.
EDIT:This is the reason theirs been so much filler. Kishi doesn't want the anime to catch up to the manga since each chapters been mostly action/fighting.