EOQ Calculator (Economic Order Quantity)
Use this tool to calculate the most cost-efficient order quantity, estimated reorder point, and annual inventory control costs.
What is EOQ and why it matters
EOQ stands for Economic Order Quantity, a classic inventory management model used to find the optimal number of units to order each time. The goal is simple: minimize the total cost of inventory by balancing two competing expenses:
- Ordering cost (placing and receiving orders)
- Holding cost (storing inventory over time)
If you order too often, ordering costs rise. If you order too much at once, storage and carrying costs rise. EOQ gives you a practical middle point.
EOQ formula explained
The standard EOQ equation is:
EOQ = √((2DS) / H)
- D = annual demand (units)
- S = ordering cost per order
- H = annual holding cost per unit
This model assumes relatively stable demand and lead time. Even when reality is messy, EOQ is still a strong baseline for decision-making.
How to use this EOQ calculator
Step 1: Enter demand and cost inputs
Add your annual demand, cost to place one order, and annual holding cost per unit. These three values are required.
Step 2: Add lead-time details
Working days, lead time, and optional safety stock are used to estimate the reorder point, which tells you when to place the next order.
Step 3: Review operational metrics
In addition to EOQ, the calculator returns order frequency, days between orders, annual ordering cost, annual holding cost, and total inventory control cost.
Interpreting your results
EOQ (units per order)
This is the order quantity that minimizes the sum of ordering and holding costs.
Orders per year
Helps with procurement planning and vendor coordination.
Days between orders
Useful for setting calendar-based replenishment cycles.
Reorder point
Estimated as daily demand × lead time + safety stock. This helps prevent stockouts while waiting for replenishment.
Worked example
Suppose a business sells 12,000 units per year, pays $75 per order, and spends $4.50 per unit annually on carrying costs:
- D = 12,000
- S = 75
- H = 4.50
EOQ = √((2 × 12,000 × 75) / 4.5) = √400,000 ≈ 632 units. That means ordering roughly 632 units each time is near-optimal under the model assumptions.
EOQ assumptions to keep in mind
- Demand is steady and known
- Lead time is relatively constant
- No stockouts are planned
- Unit price is stable (no major volume discount impact)
- Holding and ordering costs are reasonably estimated
If your operation has seasonality, uncertain lead times, or variable supplier pricing, use EOQ as a starting point and refine with real-world constraints.
Tips to improve EOQ-based inventory strategy
- Reduce ordering friction through automation and supplier portals
- Improve warehouse efficiency to lower carrying costs
- Review EOQ quarterly when demand patterns shift
- Segment SKUs using ABC analysis before applying one policy to all items
- Combine EOQ with safety stock and service-level targets
Final thoughts
EOQ calculation is one of the fastest ways to improve inventory performance with data. A few numbers can reveal where money is quietly leaking from operations. Use this calculator as your baseline, then tune your replenishment plan with actual demand behavior, supplier performance, and customer service goals.