Economic Order Quantity Explainer
Economic order quantity, or EOQ, is a model for estimating the replenishment quantity that minimizes the combined annual cost of ordering and holding inventory. Small frequent orders reduce average stock but create more ordering activity. Large orders reduce the number of orders but increase cash tied up, storage, insurance, damage, and obsolescence exposure.
The classic formula is the square root of twice annual demand multiplied by the cost per order, divided by annual holding cost per unit. The model assumes relatively stable demand and lead time, a fixed order cost, immediate replenishment, and no stockouts or quantity discounts. Under those conditions, the optimal point balances annual ordering cost with annual holding cost.
EOQ is a starting point for policy, not an automatic purchase instruction. Buyers must also consider supplier minimums, package sizes, transportation, shelf life, capacity, cash limits, service targets, and price breaks. A discount may justify a different quantity only when the merchandise savings exceed the added holding and risk costs.
The model becomes less reliable when demand is seasonal, supply is uncertain, items share order costs, or replenishment arrives gradually. Update inputs and compare the recommendation with actual operating constraints. Pair EOQ with a reorder point and safety stock, and monitor total cost, stockouts, aging, and forecast changes rather than judging performance only by order size.
Frequent orders raise ordering cost, while large orders raise holding cost.
EOQ estimates the quantity where the combined annual cost is lowest under its assumptions.
The classic model expects stable demand, stable lead time, fixed order cost, and immediate replenishment.
Seasonality, uncertainty, or shared shipments may require a different model or adjustment.
Package sizes, minimums, discounts, cash, shelf life, and storage can change the practical order quantity.
Compare any adjustment with total cost rather than purchase price alone.
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