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Effective inventory management is essential for maintaining a lean supply chain. Proper calculations help reduce excess stock, minimize costs, and improve overall efficiency. This article discusses key calculations used to optimize inventory levels.
Economic Order Quantity (EOQ)
EOQ determines the ideal order quantity that minimizes total inventory costs, including ordering and holding costs. The formula is:
EOQ = √(2DS / H)
Where:
- D = Annual demand
- S = Ordering cost per order
- H = Holding cost per unit per year
Reorder Point (ROP)
The Reorder Point indicates when new stock should be ordered to prevent stockouts. It considers lead time demand:
ROP = Lead Time Demand = Lead Time (days) × Daily Demand
Safety Stock Calculation
Safety stock acts as a buffer against demand variability and lead time delays. It is calculated based on demand fluctuations and supplier reliability.
A common formula is:
Safety Stock = Z × σd × √Lead Time
Where:
- Z = Service level factor (from Z-table)
- σd = Standard deviation of daily demand