The Ultimate Guide to Economic Order Quantity (EOQ)
Managing inventory is a constant tug-of-war. If you order too much stock at once, your warehouse fills up, and your holding costs (rent, insurance, depreciation) skyrocket. If you order too little, your holding costs drop, but your ordering costs (shipping fees, admin labor, logistics) explode because you are constantly placing tiny orders.
The Economic Order Quantity (EOQ) formula solves this dilemma. It is a Nobel-prize-winning mathematical formula that identifies the exact, optimal number of units you should order to make your total inventory costs as low as mathematically possible.
Ordering Costs (S)
Ordering costs are the fixed expenses incurred every time you place an order with your supplier, regardless of the order size. This includes flat-rate shipping, import customs processing fees, the labor cost of your procurement team cutting a Purchase Order, and receiving/unloading labor.
Holding Costs (H)
Holding costs (or carrying costs) are the expenses associated with storing unsold inventory. This includes warehouse rent, electricity, theft/shrinkage, insurance, and the opportunity cost of tying up your capital in boxes rather than investing it elsewhere. It is usually calculated as 15% to 25% of the inventory's value per year.
The EOQ Formula Explained
To calculate the EOQ by hand, you need three data points: Annual Demand (D), Ordering Cost per order (S), and Holding Cost per unit per year (H). The formula is:
EOQ = √ (2 × D × S) / H
The square root of (2 times Demand times Ordering Cost) divided by Holding Cost.
The "Perfect Balance" Principle
One of the most fascinating aspects of the EOQ model is the point of perfect equilibrium. At your exact EOQ, your Annual Ordering Cost will perfectly equal your Annual Holding Cost.
If you run our calculator and notice that your ordering cost is drastically higher than your holding cost, it means you are ordering too frequently. If your holding cost is much higher, it means you are buying too much bulk at once and wasting money on storage.
Limitations of the EOQ Model
The EOQ formula is incredibly powerful, but it makes a few strict assumptions: It assumes demand is perfectly constant throughout the year (no seasonal spikes), it assumes ordering costs are static, and it assumes no bulk-purchasing discounts exist. If your supplier offers a massive discount for ordering 10,000 units, you may choose to ignore your EOQ to capture the discount!