1. What is EOQ?
EOQ stands for Economic Order Quantity.
It is the quantity of material that should be ordered each time so that the total inventory cost becomes minimum. The EOQ model helps in minimizing total ordering cost and holding cost.
In simple words:
If a company orders too often, ordering cost becomes high.
If it orders too much at once, storage cost becomes high.
EOQ helps find the best order quantity between these two extremes.
Very easy meaning
Imagine a grocery store buying rice.
- If it orders rice every 2 days, transport, paperwork, and order cost rise.
- If it orders 6 months’ rice at once, storage cost, spoilage risk, and blocked money rise.
So the shop wants one order size that is not too small and not too big.
That best quantity is called EOQ.
2. Why EOQ is important
EOQ is important because every business must answer two practical questions:
- how much should be ordered each time?
- how can total inventory cost be reduced?
If order quantity is chosen randomly:
- stock cost may increase
- storage space may be wasted
- too many orders may be placed
- capital may get blocked
- inventory control becomes inefficient
EOQ helps a business:
- reduce total inventory cost
- make ordering systematic
- improve stock planning
- balance ordering cost and carrying cost
- avoid unnecessary excess stock
3. Main objective of EOQ
The main objective of EOQ is to determine the most economical order size.
This means the order quantity should be chosen in such a way that:
- ordering cost is not too high
- carrying cost is not too high
- total cost is as low as possible
So EOQ is basically a cost-minimizing inventory tool.
4. Basic idea behind EOQ
EOQ is based on one simple logic:
- when order quantity is small, the company places orders many times, so ordering cost becomes high
- when order quantity is large, the company stores more stock, so carrying cost becomes high
EOQ tries to find the point where these two costs are balanced in the best possible way.
Small order quantity means
- more frequent orders
- higher ordering cost
- lower average inventory
- lower carrying cost
Large order quantity means
- fewer orders
- lower ordering cost
- higher average inventory
- higher carrying cost
EOQ gives the quantity where total cost is minimum.
5. Costs involved in EOQ
EOQ mainly considers two major costs.
Ordering cost
This is the cost of placing one order.
It may include:
- paperwork
- communication
- follow-up
- transport arrangement
- receiving and inspection effort
If a company places more orders, total ordering cost increases.
Carrying cost or holding cost
This is the cost of storing inventory.
It may include:
- warehouse rent
- insurance
- interest on blocked capital
- spoilage
- deterioration
- obsolescence
- security cost
If a company keeps more stock, carrying cost increases. Carrying cost is the expense of storing inventory for a specified period of time.
Important point
EOQ mainly balances:
- ordering cost
- carrying cost
It does not mainly focus on purchase price changes in the basic model.
6. EOQ formula
The standard EOQ formula is:
EOQ = √(2DS / H)
Where:
- D = annual demand or annual usage
- S = ordering cost per order
- H = holding cost per unit per year
In your material, annual usage is identified as one of the important components used in the EOQ idea.
Meaning of the formula
This formula helps calculate the best order quantity by using:
- how much material is needed in one year
- how much one order costs
- how much it costs to hold one unit for one year
7. Simple explanation of the formula
Let us understand the formula in an easy way.
If annual demand is high
The company needs more material, so EOQ usually becomes higher.
If ordering cost is high
The company should order larger quantities less often, so EOQ increases.
If holding cost is high
The company should not keep too much inventory, so EOQ decreases.
So EOQ changes according to demand, ordering cost, and carrying cost.
8. Example of EOQ calculation
Suppose a company uses 10,000 units per year.
Ordering cost per order = ₹100
Holding cost per unit per year = ₹5
Now apply the formula:
EOQ = √(2 × 10,000 × 100 / 5)
EOQ = √(20,00,000 / 5)
EOQ = √4,00,000
EOQ ≈ 632 units
This means the most economical order quantity is about 632 units per order.
So instead of ordering randomly, the company should place orders near this quantity.
9. What EOQ tells the company
EOQ tells the company:
- how much to order each time
- how to reduce inventory cost
- how to avoid over-ordering
- how to avoid too frequent ordering
It does not directly tell when to order.
That is usually decided using:
- reorder point
- lead time
- safety stock
So:
- EOQ = how much to order
- Reorder point = when to order
This difference is very important.
10. Assumptions of the basic EOQ model
The basic EOQ model works on certain assumptions.
Demand is known and constant
The company assumes annual demand is predictable.
Ordering cost is constant
Each order costs the same to place.
Holding cost is constant
The cost of carrying one unit per year is assumed to remain stable.
Lead time is known
The time between order and receipt is assumed to be known.
No stock-outs in the basic model
The basic EOQ model usually assumes no shortage occurs.
Replenishment is immediate
The ordered stock arrives when required as planned.
These assumptions make the model simple and useful, but real life may be more complicated.
11. Graphical understanding of EOQ
EOQ is also understood with a cost graph.
Ordering cost curve
As order quantity increases, ordering cost decreases.
Why?
Because fewer orders are placed.
Carrying cost curve
As order quantity increases, carrying cost increases.
Why?
Because more stock is stored on average.
Total cost curve
Total cost first falls, then reaches the minimum point, and then rises again.
That minimum point is the EOQ point.
So EOQ is the point where total inventory cost is lowest.
12. Relationship between EOQ and average inventory
When order quantity is fixed and stock is used steadily, average inventory is usually:
Average inventory = EOQ / 2
Example:
If EOQ is 600 units, average inventory is about 300 units.
This is because stock rises to the order quantity and gradually falls as it is consumed.
13. Number of orders per year
EOQ also helps calculate how many orders are needed each year.
Formula:
Number of orders per year = Annual demand / EOQ
Example:
If annual demand = 12,000 units
EOQ = 600 units
Then:
Number of orders = 12,000 / 600 = 20 orders per year
This helps the company plan purchasing frequency.
14. Time between orders
Once EOQ is known, the company can also estimate the time gap between orders.
Formula idea:
Time between orders = Working period / Number of orders per year
Example:
If the company works 300 days a year and places 20 orders:
300 / 20 = 15 days
So one order may be placed every 15 days.
This helps link EOQ to practical purchase planning.
15. Advantages of EOQ
EOQ provides many benefits.
Reduces total inventory cost
It balances carrying cost and ordering cost.
Improves ordering decisions
The company gets a scientific order size instead of relying on guesswork.
Prevents over-ordering
It avoids unnecessary large stock accumulation.
Prevents too frequent ordering
It avoids the waste of placing too many small orders.
Supports better inventory planning
EOQ helps purchase, stores, and inventory departments work more systematically.
Easy to understand and use
The model is simple and widely used.
16. Limitations of EOQ
EOQ is useful, but it has limitations.
Demand may not remain constant
In real life, demand may rise or fall.
Holding cost may change
Warehouse cost, interest, and insurance may vary.
Ordering cost may not be fixed
Different suppliers or situations may create different order costs.
Lead time may not be stable
Suppliers may delay unexpectedly.
Basic EOQ ignores shortages
The simple model assumes no stock-out.
Purchase discounts are not considered in the basic model
Bulk buying discounts may change the decision.
So EOQ is a very helpful model, but it should be used with practical judgment.
17. EOQ and reorder point
Students often confuse these two.
EOQ
EOQ tells how much to order.
Reorder point
Reorder point tells when to place the order.
Example:
- EOQ may be 500 units
- reorder point may be 150 units
That means when stock falls to 150 units, the company places a new order of 500 units.
So both are used together in inventory control.
18. EOQ and safety stock
EOQ decides the best order size.
Safety stock is extra stock kept for uncertainty.
These two are related but different.
Example:
- EOQ = 400 units
- safety stock = 50 units
This means the company orders 400 units each time, but also keeps 50 extra units as protection.
So EOQ works better when combined with safety stock and reorder planning.
19. EOQ in real business
EOQ can be used in many kinds of organizations.
Manufacturing
A factory may use EOQ for:
- steel
- screws
- packing materials
- spare parts
Retail
A shop may use EOQ for:
- notebooks
- groceries
- packaged goods
Hospitals
EOQ may be used for:
- gloves
- syringes
- medicines with stable demand
So EOQ is not only for factories. It is useful wherever stock is ordered regularly.
20. EOQ with shortage concept
In advanced inventory models, shortage may also be allowed.
Your material mentions a purchasing model with shortages and refers to shortage cost in such models. It also notes that when shortage cost tends toward zero, the shortage model can transform toward a no-shortage form.
In simple terms:
- the basic EOQ model assumes no shortage
- advanced models may allow limited shortage if it is economical
But for basic MBA understanding, the main focus is the no-shortage EOQ model.
21. When EOQ is most useful
EOQ is most useful when:
- demand is fairly stable
- inventory is used regularly
- ordering cost is known
- holding cost is known
- shortage is not desirable
- purchase quantity needs to be planned scientifically
So EOQ works best in regular and predictable inventory situations.
22. Difference between EOQ and ABC analysis
EOQ
EOQ tells the best order size.
ABC analysis
ABC analysis tells which items need more control based on value.
So:
- EOQ = order quantity decision
- ABC = item classification decision
Both are inventory tools, but they do different jobs.
23. Difference between EOQ and inventory management
Inventory management is the full system of stock planning and control.
EOQ is one specific technique used inside inventory management.
So:
- inventory management = broad concept
- EOQ = one important tool
24. Simple exam-style answer
Economic Order Quantity (EOQ) is the order quantity that minimizes the total inventory cost by balancing ordering cost and carrying cost. It helps a company determine the most economical quantity to order each time. The standard EOQ formula is √(2DS/H), where D is annual demand, S is ordering cost per order, and H is holding cost per unit per year. EOQ reduces total inventory cost, improves ordering decisions, and supports better inventory planning. However, the basic EOQ model assumes constant demand, constant costs, known lead time, and no shortages.
25. Very easy memory version
EOQ means the best order quantity that keeps total inventory cost as low as possible.
Remember these keywords:
- ordering cost
- carrying cost
- annual demand
- best order size
- minimum total cost
26. Final easy example
Suppose a college stationery store sells pens regularly throughout the year.
If it orders very small quantities again and again:
- ordering effort increases
If it orders too many pens at once:
- storage increases
- money gets blocked
So the store calculates one ideal order size that is neither too small nor too large.
That ideal size is called EOQ.
