Calculate the exact buffer inventory you need to protect your operations against demand spikes and supply delays, without locking up excess capital.
Enter your demand variability and lead time data. The calculator returns the optimal safety stock and your exact reorder point for your target service level.
Safety stock is the additional inventory you hold above your expected demand during lead time to act as a buffer against two types of variability: demand variability (customers ordering more than expected) and supply variability (suppliers delivering later than expected). Without safety stock, any upward spike in demand or delay in supply will cause a stockout.
In Pakistan's supply chain environment, where lead time variability is high, supplier reliability is inconsistent, and stockout costs are significant, properly calculated safety stock is one of the most important decisions a supply chain manager can make.
This calculator uses the standard safety stock formula: SS = (Max Daily Demand ร Max Lead Time) โ (Avg Daily Demand ร Avg Lead Time). The reorder point is then: ROP = (Avg Daily Demand ร Avg Lead Time) + SS.
Higher service level targets require more safety stock. A 99% service level means you can meet demand without stockout 99% of the time, but it requires holding significantly more buffer inventory. For most Pakistan SMEs, 95% is the right starting target, balancing service reliability against working capital cost.
A distributor of imported spare parts has average demand of 45 units a day (peaking at 70), and an average lead time of 18 days (peaking at 30 during port delays). Safety Stock = (70 ร 30) โ (45 ร 18) = 2,100 โ 810 = 1,290 units, with a reorder point of 810 + 1,290 = 2,100 units.
Covers variability in both demand and lead time simultaneously.
The inventory trigger level, when to place the next order.
More precise method using standard deviations and service level Z-scores.