EOQ Calculator (Economic Order Quantity)

About the EOQ Calculator (Economic Order Quantity)

Economic Order Quantity (EOQ) is the order size that minimizes the combined annual cost of ordering inventory and holding it in stock. The classic Wilson formula balances two opposing forces: ordering costs that decrease as order sizes grow (fewer orders per year) and carrying costs that increase as order sizes grow (more average inventory on hand).

Manufacturers and distributors use EOQ to determine how much raw material or finished goods to purchase in each replenishment cycle. By ordering the EOQ quantity each time, a company achieves the lowest possible total inventory cost under stable demand and cost assumptions. Deviations from EOQ — ordering too much or too little — always result in higher combined costs.

This calculator applies the standard EOQ formula so you can quickly find the optimal order quantity, the number of orders per year, and the resulting total annual cost for any item in your inventory.

Tracking this metric consistently enables manufacturing teams to identify performance trends early and take corrective action before minor inefficiencies escalate into significant production losses.

When This Page Helps

Ordering too frequently wastes money on purchase orders, receiving labor, and freight surcharges. Ordering too much ties up cash and warehouse space while increasing risk of obsolescence. EOQ finds the mathematical sweet spot, giving you a defensible, data-driven order quantity that minimizes total cost.

How to Use the Inputs

1. Enter annual demand — the total units consumed or sold per year.
2. Enter the cost per order — freight, admin, receiving, and inspection costs for one purchase order.
3. Enter the annual carrying cost per unit — storage, insurance, capital, and obsolescence cost for holding one unit for a year.
4. Review the calculated EOQ, orders per year, and total annual cost.
5. Adjust inputs to model scenarios like demand changes or supplier minimum order quantities.
6. Round the EOQ to a practical pack size or container quantity if needed.

Example Calculation

Tips & Best Practices

• Include all ordering costs: purchase order processing, freight, receiving, and quality inspection.
• Carrying cost typically runs 20-30% of item value per year — include capital cost, warehousing, insurance, and obsolescence.
• Recalculate EOQ when demand, supplier pricing, or warehouse costs change significantly.
• If the EOQ is much smaller than a supplier's minimum order, negotiate or consider alternative sourcing.
• Use EOQ as a starting point, then adjust for real-world constraints like shelf life, container sizes, and volume discounts.
• Combine EOQ with safety stock and reorder point calculations for a complete replenishment policy.

Understanding the Cost Trade-Off

The fundamental insight behind EOQ is that ordering costs and carrying costs move in opposite directions as order size changes. Larger orders mean fewer purchase orders per year (lower ordering costs) but higher average inventory on hand (higher carrying costs). EOQ is the quantity where these two cost curves intersect, yielding the lowest total.

Practical Adjustments

Real supply chains rarely match EOQ assumptions perfectly. Lead times, demand fluctuations, quantity discounts, and container sizes all influence the actual order quantity. Use EOQ as a baseline and adjust for practicalities like rounding to pallet quantities or meeting supplier minimums.

EOQ in Lean Manufacturing

Lean practitioners often aim to reduce both ordering costs and carrying costs simultaneously — for example, by negotiating blanket purchase orders (lower S) and implementing just-in-time delivery (lower H). As both costs fall, the EOQ gets smaller, enabling more frequent, smaller deliveries that reduce waste and improve cash flow.

Frequently Asked Questions

• What does EOQ stand for?

  EOQ stands for Economic Order Quantity. It is the order quantity that minimizes the sum of ordering costs and carrying costs over a given period, typically one year.

• What assumptions does the EOQ model make?

  The classic EOQ model assumes constant, known demand; fixed ordering cost per order; fixed carrying cost per unit per year; instantaneous replenishment (no lead time shortages); and no quantity discounts. Real-world adjustments relax these assumptions.

• How does demand variability affect EOQ?

  The basic EOQ formula uses average demand. If demand is highly variable, you should pair EOQ with a safety stock calculation to buffer against stockouts during lead time.

• Can EOQ be used for manufactured items?

  Yes. For manufactured items, replace ordering cost with setup cost (the cost to set up a production run). The formula becomes the Economic Production Quantity (EPQ), which also accounts for the production rate.

• What if carrying cost is expressed as a percentage?

  Convert it to dollars per unit per year by multiplying the percentage by the unit cost. For example, a 25% carrying rate on a $10 item yields H = $2.50 per unit per year.

• How do quantity discounts affect EOQ?

  When suppliers offer price breaks at higher volumes, you must compare the total cost at the EOQ with the total cost at each discount break quantity. Sometimes ordering more than the EOQ saves money overall because the unit price drop outweighs the higher carrying cost.

• How often should I recalculate EOQ?

  Recalculate quarterly or whenever significant changes occur in demand, material prices, warehouse costs, or ordering costs. Many ERP systems recalculate automatically during each MRP run.

• What is the relationship between EOQ and reorder point?

  EOQ tells you how much to order; the reorder point tells you when to order. They work together: when inventory drops to the reorder point, you place an order for the EOQ quantity.