Economic Order Quantity (EOQ) Calculator
Use this tool to estimate the ideal order size that minimizes annual ordering and holding costs.
What is EOQ?
EOQ stands for Economic Order Quantity. It is a classic inventory management formula used to find the order size that minimizes two competing costs:
- Ordering costs (placing and receiving purchase orders)
- Holding costs (storing inventory over time)
If you order too often, your ordering costs rise. If you order in very large batches, your holding costs increase. EOQ gives a practical middle ground.
EOQ Formula
The standard EOQ formula is:
EOQ = √((2 × D × S) / H)
Where:
- D = annual demand (units per year)
- S = ordering cost per order
- H = annual holding cost per unit
This calculator also estimates related planning values such as number of orders per year, cycle length, and reorder point (when working days and lead time are provided).
How to Use This EOQ Calculator
1) Enter your demand
Add annual demand in units. This should be a realistic yearly estimate from sales history or forecast data.
2) Enter ordering cost
Include all costs tied to creating and processing one order: admin time, communication, receiving, inspection, and setup.
3) Enter holding cost
Holding cost per unit per year may include warehousing, insurance, shrinkage, obsolescence, and cost of capital.
4) Optional planning inputs
Working days and lead time let you estimate cycle time and reorder point. This helps convert EOQ from theory into day-to-day purchasing decisions.
Worked Example
Suppose:
- Annual demand (D): 12,000 units
- Ordering cost (S): $55 per order
- Holding cost (H): $3.20 per unit per year
EOQ = √((2 × 12,000 × 55) / 3.2) ≈ 642 units per order. That means ordering roughly 642 units each time should minimize your annual ordering + holding costs under the EOQ model assumptions.
Why EOQ Matters for Operations and Finance
- Improves cash flow: Avoids tying too much cash into inventory.
- Cuts avoidable cost: Balances purchase frequency and inventory carrying cost.
- Supports planning: Helps buyers and planners set consistent replenishment policies.
- Creates a baseline: Useful as a starting policy before adding safety stock and service-level targets.
Important EOQ Assumptions
EOQ is most accurate when these conditions are approximately true:
- Demand is relatively stable and predictable.
- Lead time is known and not highly variable.
- Unit purchase price is constant (no large quantity discounts).
- Orders arrive in full batches at once.
- Stockouts are not allowed in the basic model.
In real businesses, demand and lead times often vary. So EOQ is best used as a decision framework, then adjusted using safety stock, service-level goals, and practical supplier constraints.
EOQ vs. Reorder Point
These two terms are often confused:
- EOQ tells you how much to order.
- Reorder Point (ROP) tells you when to place the order.
Basic ROP formula used in this tool: ROP = Daily Demand × Lead Time (days).
Practical Tips for Better Inventory Decisions
- Review EOQ quarterly for high-volume SKUs.
- Segment products (A/B/C analysis) and apply stricter control to high-value items.
- Track forecast error; poor forecasts reduce EOQ usefulness.
- Consider MOQ (minimum order quantity) and supplier packaging constraints.
- Layer EOQ with safety stock to protect customer service levels.
Final Thoughts
A good EOQ calculator helps you move from guesswork to data-driven inventory control. Even if your environment is complex, EOQ gives you a strong baseline for cost optimization, purchasing discipline, and working-capital management.