A sheet stacking apparatus includes a lowering control unit to lower a sheet stacking portion, a determination unit, an acquisition unit, an identification unit, and a notification unit. The determination unit determines that the sheet stacking portion cannot be lowered by the lowering control unit. The acquisition unit acquires a position of the sheet stacking portion at which the determination unit determines that the sheet stacking portion cannot be lowered. The identification unit identifies an amount of sheets stackable on the sheet stacking portion without removing an obstacle placed under the sheet stacking portion based on the position acquired by the acquisition unit. The notification unit notifies the amount of sheets identified by the identification unit and an amount of sheets stackable on the sheet stacking portion after removal of the obstacle placed under the sheet stacking portion.