What are Inventory Management Models?
Inventory management models help businesses optimize stock levels by balancing ordering costs against holding (storage) costs. Key models include the Economic Order Quantity (EOQ), just-in-time (JIT) systems, and ABC analysis, each suited to different demand and cost scenarios.
Inventory models optimize order quantity and timing. EOQ (Q = √(2DS/H)) calculates the order size minimizing total cost. JIT minimizes stock by receiving goods just before use. ABC analysis categorizes items by value (A = high value, C = low value), applying different control strategies to each.
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Step-by-step worked examples
A store needs 5000 units annually. Order cost is €50 per order, holding cost €2 per unit per year. Calculate EOQ.
EOQ = √(2DS/H) EOQ = √((2 × 5000 × 50) / 2) EOQ = √(250000) ≈ 500 units
Using the EOQ of 500 units from above, how many orders are needed annually?
Number of orders = D / EOQ Orders = 5000 / 500 = 10 orders per year
A retailer uses ABC analysis. Product A (high-value) has 500 units in stock; Product C (low-value) has 5000 units. If A uses 80% of capital, what does C represent?
ABC analysis: A = ~10% of items, 80% of value B = ~20% of items, 15% of value C = ~70% of items, 5% of value Product C represents bulk, low-value stock
Flashcards
Quick quiz
Q1.EOQ = √(2DS/H). If D=10k, S=100, H=5, what is EOQ?
Q2.JIT inventory minimizes ___.
Q3.In ABC analysis, A items are ___.
Q4.If EOQ is 300 units and annual demand is 6000 units, order frequency is…
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Common mistakes
Confusing EOQ with actual order quantity used. — Correct: EOQ is the optimal order size; actual orders may vary based on supplier constraints, demand variability, and lead times.
Thinking JIT eliminates all inventory. — Correct: JIT minimizes but doesn't eliminate inventory — safety stock is often kept for demand uncertainty and supply disruptions.
Applying same control to all inventory items. — Correct: ABC analysis allocates resources: strict control for A (high-value), relaxed for C (low-value).
Ignoring lead time in EOQ decisions. — Correct: Reorder point = lead time × daily demand. EOQ doesn't capture lead time variability.
FAQ
What is the Economic Order Quantity formula?
EOQ = √(2DS/H), where D = annual demand, S = order cost per order, H = annual holding cost per unit.
When is EOQ most useful?
EOQ works best for items with relatively constant demand, predictable lead times, and measurable ordering and holding costs.
What is the difference between EOQ and ABC analysis?
EOQ determines order size for a single item. ABC categorizes all inventory by value, applying different strategies to each category.
Can EOQ and JIT be used together?
Yes — JIT principles apply broadly, while EOQ can optimize batch sizes for items that aren't on full JIT systems.