Item stack size

Solid items have defined stack size. Within the stack size, multiple items of the same kind are automatically grouped into a single slot in engineer's or building's inventory. If more than that, items are overflowed into the next slot.

• Most production buildings have only 1 slot for each kind of input and output items. If any of the the output stack is full, the building will pause until the slot is not full.
• Storages and vehicles generally have multiple slots to store large amount of items.
• Dropped items always attempt to group in stacks.
• Most equipment do not stack - they have stack size of 1.
• The stack size of solid items can be 1, 50, 100, 200, or 500.

Fluids do not have a defined stack size under normal circumstances - they must be contained in a pipeline. Its packaged form, however, can be stacked like other solid items.

• In many fluid-related buildings such as a Refinery, they are limits to the buildings input and output fluid slot, measured in m³.
• Certain glitches allow the fluid to be contained in slots, such as when dismantling a Freight Car loaded with fluid.

Splitting stack

In the inventory window Tab ↹, to split a stack into halves. Holding down on the stack enables custom splitting, use the slider or manual input the desired number of split item.