Minecraft wiki entry for Chest, associated text: The capacity of a chest varies greatly, depending on its size, whether the items inside it are stackable, and whether shulker boxes are used. The minimum capacity is obtained when storing only non-stackable items while the maximum capacity can be achieved when storing items that stack to 64. Filled shulker boxes are not stackable, but each can hold 27 stacks of up to 64 items (excluding other shulker boxes), so filling a chest with them increases the maximum by a factor of 27.