Economic Order Quantity (EOQ)

A decision model that determines the optimum order size for purchasing or manufacturing an item in stock, balancing ordering and holding costs.

Definition

Economic Order Quantity (EOQ) is a decision model used in inventory management to determine the ideal order size that minimizes the total cost of inventory. The EOQ model calculates the optimal quantity of stock that should be purchased or produced to minimize the combined total cost of ordering and holding inventory. The classic EOQ formula is:

\[ EOQ = \sqrt{\frac{2cd}{h}} \]

where:

  • Q is the quantity to be purchased or manufactured.
  • c is the cost of processing an order for delivery.
  • d is the demand in the period for that stock item.
  • h is the cost of holding a unit of stock per period.

Examples

  1. Manufacturing Scenario: A manufacturing company requires raw materials to produce its goods. The company has calculated that the cost of placing an order (c) is $50, the annual demand (d) is 10,000 units, and the holding cost per unit per year (h) is $2. Using the EOQ formula:

    \[ EOQ = \sqrt{\frac{2 \times 50 \times 10,000}{2}} = \sqrt{500,000} = 707 \text{ units (rounded)} \]

    Thus, the company should order 707 units each time to minimize costs.

  2. Retail Scenario: A retail store sells electronic gadgets. The store knows that the ordering cost is $100 per order, the annual demand is 3,600 units, and the holding cost per unit per year is $5. Using the EOQ formula:

    \[ EOQ = \sqrt{\frac{2 \times 100 \times 3,600}{5}} = \sqrt{144,000} = 379 \text{ units (rounded)} \]

    To minimize costs, the store should order 379 units each time.

Frequently Asked Questions (FAQs)

Q: What are the primary assumptions of the EOQ model? A: The EOQ model assumes that the demand rate is constant, the order lead time is fixed, the replenishment is instantaneous, and the holding and ordering costs are constant.

Q: How is EOQ different from Economic Batch Quantity (EBQ)? A: EOQ typically refers to the optimum order size for purchasing items, while EBQ (Economic Manufacturing Quantity) or EBQ (Economic Batch Quantity) refers to the optimal production batch size for manufacturing.

Q: Can EOQ be used for perishable goods? A: EOQ is not typically used for perishable goods due to their shelf-life constraints. Models like the Perishable Inventory Management (PIM) are more appropriate for such items.

Q: What is the impact of discount policies on EOQ? A: Quantity discounts can influence the EOQ calculation by reducing the cost per unit, which might lead to adjustments in the order size to take advantage of the lower price.

  • Economic Batch Quantity (EBQ): Similar to EOQ, but used for determining the optimal batch size for manufacturing, considering setup costs and holding costs.
  • Reorder Point: The inventory level at which a new order should be placed to avoid stockouts.
  • Holding Costs: Costs associated with storing inventory, including warehousing, insurance, and spoilage.
  • Ordering Costs: Costs related to placing and receiving orders, including administrative and shipping expenses.
  • Safety Stock: Additional inventory held to protect against uncertainties in demand or supply.

Online References

Suggested Books for Further Studies

  • “Production and Operations Analysis” by Steven Nahmias: Discusses production analysis techniques including EOQ and its variations.
  • “Inventory Management and Production Planning and Scheduling” by Edward Silver, David Pyke, and Rein Peterson: Comprehensive coverage of inventory management, including EOQ models.
  • “Principles of Operations Management: Sustainability and Supply Chain Management” by Jay Heizer and Barry Render: Offers insights on EOQ within the context of broader operations management.

Accounting Basics: “Economic Order Quantity (EOQ)” Fundamentals Quiz

### Which statement best describes the EOQ model? - [ ] A model used for financial forecasting. - [ ] A strategy for pricing products. - [xx] A decision model to determine the optimum order size for inventory. - [ ] A process for improving the quality of goods. > **Explanation:** The EOQ is specifically designed to determine the optimal order size that minimizes the sum of ordering and holding costs in inventory management. ### What is the primary goal of the EOQ model? - [ ] To increase sales. - [ ] To reduce lead times. - [x] To minimize the total cost of ordering and holding inventory. - [ ] To maximize production output. > **Explanation:** The EOQ model aims to find the order quantity that minimizes the total costs associated with ordering and holding inventory. ### In the EOQ formula, what does the variable 'c' represent? - [ ] Demand in the period for the item. - [x] Cost of processing an order. - [ ] Holding cost per unit of stock. - [ ] Total sales revenue. > **Explanation:** In the EOQ formula, 'c' specifically stands for the cost of processing an order. ### How does an increase in the holding cost (h) affect the EOQ? - [x] It decreases the EOQ. - [ ] It increases the EOQ. - [ ] The EOQ remains the same. - [ ] It has no predictable effect. > **Explanation:** As holding costs increase, keeping inventory becomes more expensive, thus reducing the EOQ. ### If the demand (d) for a product doubles, what happens to the EOQ? - [ ] EOQ is halved. - [ ] EOQ remains the same. - [x] EOQ increases. - [ ] EOQ is doubled. > **Explanation:** As demand increases, the EOQ also increases, but not at the same rate due to the square root function in the EOQ formula. ### Can EOQ be applied to perishable goods? - [ ] Yes, without any adjustments. - [ ] Yes, but with a different formula. - [x] No, because of their limited shelf life. - [ ] It depends on the situation. > **Explanation:** EOQ is generally not suitable for perishable goods due to their limited shelf life and specific waste considerations. ### Who primarily uses the EOQ model? - [ ] Personal shoppers. - [x] Inventory managers. - [ ] Financial auditors. - [ ] Marketing executives. > **Explanation:** Inventory managers usually utilize the EOQ model to optimize order sizes and control inventory costs. ### What is one major assumption of the EOQ model? - [x] Demand rate is constant. - [ ] Demand rate is highly variable. - [ ] Prices are deeply discounted. - [ ] Holding cost is negligible. > **Explanation:** One major assumption of the EOQ model is that the demand rate for the stock item is constant. ### What type of costs are balanced through the EOQ calculation? - [ ] Selling and administrative costs. - [ ] Shipping and deflation costs. - [xx] Ordering and holding costs. - [ ] Variable and fixed costs. > **Explanation:** The EOQ model balances ordering costs (costs incurred to place orders) and holding costs (costs for storing inventory). ### In a scenario with quantity discounts, how should the EOQ be adjusted? - [x] Reevaluate to potentially increase order size for lower per-unit costs. - [ ] Reduce the order size to boost frequency. - [ ] Disregard EOQ calculations. - [ ] Maintain current EOQ unaffected. > **Explanation:** Quantity discounts can justify increasing the EOQ to take advantage of lower per-unit costs, thereby requiring a reevaluation of the optimal order size.

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Tuesday, August 6, 2024

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