Safety stock is inventory held above expected demand during replenishment to protect against uncertainty, such as variable supplier delivery times or fluctuating consumption in a Kanban loop.
In practice, the calculation starts with demand during the measured replenishment interval. For an illustrative Kanban loop consuming 400 units per shift with a replenishment time of 0.2 shift, expected demand during replenishment is 80 units. A 50% safety allowance adds 40 units. With 20 units per container, the loop requires six cards: four covering expected demand and two providing protection. That percentage allowance does not establish a service level.
A statistical approach relates the buffer to observed variability and an agreed service target. When lead-time demand is approximately normally distributed, safety stock can be calculated as SS = z × σDL, where z is the factor associated with the target cycle service level and σDL is the standard deviation of demand accumulated during replenishment. Cycle service measures the proportion of replenishment cycles without a stockout. Fill rate measures the proportion of requested units supplied from available stock.
Safety stock supports Kanban sizing and replenishment decisions. Value Stream Mapping helps define the replenishment loop, while Pilot Testing checks whether the proposed inventory allowance covers observed demand. Kök Neden Analizi distinguishes insufficient coverage from failures such as missed signals. A Kontrol Planı assigns responsibility for reviewing the buffer when demand patterns or replenishment arrangements change.
