EOQ Calculator (Economic Order Quantity)

The EOQ model relies on a square root mathematical formula that balances annual demand against fixed ordering costs and variable holding costs. The standard equation is expressed as: EOQ = square_root((2 * D * S) / H), where D represents the annual demand quantity in units, S is the fixed cost per order (setup or administrative costs), and H is the annual holding cost per unit (storage, insurance, and depreciation). As ordering costs or demand increases, the recommended batch size rises; conversely, higher holding costs penalize large stockpiles, driving the optimal order size down.

Imagine a regional bicycle retailer that sells 10,000 replacement inner tubes every year (Yearly Demand D = 10,000). Every time the purchasing department places a new replenishment batch with the supplier, it incurs a flat administrative and shipping fee of $50 (Order Cost S = 50). Once delivered, storing each inner tube in the warehouse costs $2 per year in rent and climate control (Holding Cost H = 2). Plugging these values into our formula gives us: EOQ = square_root((2 * 10000 * 50) / 2). First, multiply the numerator: 2 * 10,000 * 50 = 1,000,000. Next, divide by the holding cost: 1,000,000 / 2 = 500,000. Finally, take the square root of 500,000, which yields approximately 707.11 units. Rounding to the nearest whole number, the business should order 707 inner tubes per batch to minimize total inventory costs.

To get the most accurate results from your inventory calculations, ensure your holding cost includes all associated overhead such as capital tied up in inventory, warehouse insurance, and shrinkage. Remember that the classic EOQ model assumes a constant demand rate and immediate replenishment, so you should build in safety stock buffers if your supply chain experiences volatile lead times or seasonal demand spikes.