Minecraft wiki entry for Beginner%27s_guide, associated text: The hotbar and main inventory add up to 36 slots for general storage, which is the limit for how much a player can carry around and transport on their person. There is no sense of "weight" or encumbrance for items; a player moves at normal speed regardless of how full their inventory is, or what particular items they are carrying. (It is a running joke that a player can bounce around while carrying what "should be" hundreds of tons of stone and/or metal.) If your inventory becomes completely full, you cannot pick up new items, although you may still be able to pick up more of any stackable items that you already have.