Minecraft Stacks and Shulker Boxes
Not every item stacks up to 64: some cap at 16 and others do not stack at all. That difference in stack size is what makes two piles with the "same item count" take up completely different amounts of inventory space.
A shulker's capacity here is 27×64=1728 items; dividing 10000 by 1728 gives 5 full shulkers with a remainder, matching the breakdown.
With stack 16, the same slot count holds far fewer items: a 54-slot double chest would hold only 54×16=864 units, versus 54×64=3456 for a full-stack item.
54 slots × 64 items per stack: this is the theoretical maximum capacity of a double chest holding the game's most common stack-size item.
A shulker box has 27 slots. With items that stack to 64, that is 27 × 64 = 1,728 items. With stack-16 items it is 432; with non-stackable items, only 27, one per slot.
27 slots, the same as a single chest. A double chest has 54, exactly double. How many items fit depends only on the stack size of whatever item is stored.
It is a fixed, non-configurable per-item-type game limit: egg, snowball and sign, among others, cap at a 16-item stack instead of the standard 64. Unique items like tools and armor go further, capping at a 1-item stack.
Divide the total quantity by the container's capacity (slots × the item's stack size): a double chest holding stack-64 items fits 3456 units; any remainder above an exact multiple rounds up to the number of full chests actually needed.
One full slot per unit, no exceptions: tools, armor, potions and filled buckets never combine into the same slot, so storing 27 of them already fills an entire shulker box, even though 27 is a small item count.
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