Supply Chain Assignment Help: EOQ, Safety Stock and Forecasting
How to calculate EOQ, safety stock, reorder points and simple forecasts, with worked examples.
What supply chain assignments usually ask
Supply chain and operations management assignments tend to combine a calculation with a short written argument. The calculations are usually inventory models and forecasts. The writing explains what the numbers mean for a real company. This guide covers the calculations that come up most.
1. Economic Order Quantity (EOQ)
EOQ is the order size that gives the lowest total of ordering cost and holding cost.
EOQ = √(2 × D × S ÷ H)
- D is annual demand in units
- S is the cost of placing one order
- H is the cost of holding one unit for a year
Worked example (made-up numbers). Annual demand is 12,000 units, each order costs $50 to place, and holding one unit for a year costs $2.
EOQ = √(2 × 12,000 × 50 ÷ 2) = √600,000 ≈ 775 units per order.
That means about 12,000 ÷ 775 ≈ 15.5 orders a year. The model assumes steady demand and a fixed cost per order, so say so in your answer and note where real life differs.
2. Reorder point and safety stock
The reorder point is the stock level that triggers a new order.
Reorder point = (average daily demand × lead time) + safety stock
Safety stock protects you against demand swings during the lead time:
Safety stock = z × σ(daily demand) × √(lead time in days)
Worked example (made-up numbers). Average demand is 40 units a day, the standard deviation of daily demand is 20, lead time is 9 days, and you want a 95% service level (z ≈ 1.65).
- Safety stock = 1.65 × 20 × √9 = 1.65 × 20 × 3 = 99 units
- Reorder point = (40 × 9) + 99 = 459 units
A higher service level means a larger z and more safety stock, which means more holding cost. A good answer explains that trade-off.
3. Simple demand forecasting
Moving average. Average the last few periods. With monthly sales of 120, 130, 125 and 140, a three-month moving average for the next month is (130 + 125 + 140) ÷ 3 ≈ 131.7.
How good is the forecast? Compare the forecast with what actually happened:
- MAD (mean absolute deviation) is the average size of the errors
- MAPE (mean absolute percentage error) shows the error as a percentage of actual demand
Say which measure you used and why. Lower is better, but a forecast that looks great on old data can still fail when conditions change.
Writing the analysis, not just the numbers
Markers usually reward the reasoning more than the arithmetic. For each calculation:
- State the formula and the assumptions.
- Show the working with units.
- Say what the result means for the business.
- Name one limitation, for example unstable demand or unreliable suppliers.
Mistakes that cost marks
- Mixing units, such as monthly demand with annual holding cost.
- Forgetting that EOQ assumes constant demand.
- Using the wrong z-value for the service level.
- Stopping at the number with no interpretation.
- Missing the link to a real company when the brief asks for one.
Common questions
What does EOQ tell you? It gives the order quantity that minimises the total of ordering and holding costs, assuming steady demand and fixed costs per order.
What is the difference between safety stock and reorder point? Safety stock is the extra buffer against uncertainty. The reorder point is the stock level that triggers an order, and it includes the safety stock.
Which forecasting method should I use? It depends on the data. A moving average suits stable demand. If there is a trend or seasonality, your course probably expects a method that accounts for it, so check your lecture notes and the assignment brief.
Can you help with a supply chain or operations assignment? Yes. Our supply chain experts can explain the methods, check your calculations and give feedback. You can message us on WhatsApp for a quote, with free rework or a refund if the work does not meet your brief.