What Is Economic Order Quantity (EOQ) and How to Calculate It

Product-heavy small businesses are facing intense inventory pressure in 2026, with carrying costs running 20 to 30 percent of inventory value per year and tariff policy pushing brands to stockpile rather than trim. That tension, rising holding cost on top of bigger order quantities, is exactly the trade-off Economic Order Quantity was built to resolve. EOQ is an inventory formula that tells you the order size that minimizes the combined cost of placing orders and holding stock. In a year where getting that answer wrong is more expensive than usual, it is worth revisiting what the formula does, what inputs you need, and when it quietly breaks down.

What is Economic Order Quantity, and what problem does it solve?

Economic Order Quantity is the order quantity that minimizes the total cost of buying and holding inventory for a given SKU over a year. It balances two costs that move in opposite directions. Ordering cost is the fixed work of placing and receiving each purchase order, so the more often you order, the higher your annual ordering cost. Holding cost is the expense of keeping units on a shelf, so the larger each order, the higher your annual holding cost. EOQ is the order size where those two lines cross.

The reason brands still care about a formula from 1913 is that both of those cost lines have gotten steeper. Ordering cost includes the people, systems, and freight work of an inbound shipment, all of which have risen with wages and drayage. Holding cost includes warehousing fees, insurance, obsolescence, and capital tied up in stock, which compounds as interest rates stay high and shrinkage climbs. EOQ does not guess at the answer. It tells you exactly where the minimum sits.

How do you calculate EOQ?

The EOQ formula is: EOQ equals the square root of (2 x D x S) divided by H. D is annual demand in units. S is the fixed ordering cost per order in dollars. H is the annual holding cost per unit in dollars.

For example, say you sell 12,000 units of a product per year, each purchase order costs $75 to place and receive, and your annual holding cost per unit is $3. Multiply 2 times 12,000 times 75 to get 1,800,000. Divide by 3 to get 600,000. Take the square root. Your EOQ is roughly 775 units per order. You would place about 15.5 orders per year, or one every 24 days, and your combined ordering plus holding cost hits its lowest point at that cadence.

What inputs does EOQ need, and where do you pull them from?

Annual demand comes from trailing 12 month sales, adjusted for any known growth rate or channel change. For a growing brand, blend the last four quarters with a forecast rather than just looking backward. This is where demand forecasting accuracy makes or breaks EOQ output.

Ordering cost per order covers everything that does not scale with order size. PO creation time, vendor communication, receiving and put-away labor, inbound freight that is billed flat, and the slice of your WMS and accounting spend tied to each PO. Most brands land between 25 and 150 dollars per order. If you have never measured it, total your purchasing and receiving costs for a quarter and divide by the number of POs processed in that quarter.

Annual holding cost per unit is the part most brands get wrong. It is not just storage. It includes storage fees, insurance, capital cost (what else that money could earn), obsolescence risk, and shrinkage. Carrying cost is typically 20 to 30 percent of a unit's landed cost per year. If your landed cost is $10, budget $2 to $3 per unit per year as the H input.

When does EOQ work well, and when does it break down?

EOQ assumes four things: demand is steady throughout the year, unit cost is constant regardless of order size, lead times are predictable, and no stockouts are tolerated. Where those hold roughly true, EOQ is hard to beat. Stable replenishment SKUs, consumables, and mature catalog items fit the assumptions well.

EOQ breaks down on seasonal SKUs, launch items, volume-discount tiers, and perishables. If you are ordering a swimsuit line for summer, raw EOQ math will tell you to place nine small orders, which is useless. If your supplier gives a 10 percent discount at 2,000 units but EOQ says 775, the quantity-discount math often beats EOQ. If lead time doubles randomly, EOQ without a safety stock buffer will stock you out. Treat EOQ as a starting point for your top 50 or so SKUs by velocity, then override it for the edge cases.

How does EOQ compare to safety stock, reorder point, and inventory days on hand?

EOQ tells you how much to order. It does not tell you when. That is where reorder point and safety stock come in. A reorder point is the inventory level that triggers the next purchase order. Safety stock is the buffer you hold above average demand to absorb lead-time and demand variability. A clean replenishment system uses EOQ as the order quantity, a reorder point as the trigger, and safety stock as the protection.

Inventory days on hand is the backward-looking metric that tells you whether the system is working. DOH divides current inventory by average daily sales to give you how many days of supply you are sitting on. If EOQ and your reorder point are tuned correctly, DOH stays inside a narrow band. If DOH is creeping up, your order quantity is too high or demand is softening. If DOH is dropping fast, safety stock is taking the hit and a stockout is coming. See our guide to inventory days on hand for the formula and 2026 benchmarks.

How do tariffs and 2026 supply chain pressure change EOQ?

Three 2026 dynamics touch the EOQ inputs directly. First, landed cost per unit has moved in large steps as IEEPA tariffs hit importers, which raises both H (holding cost per unit) and the stakes of holding too much. Second, ordering cost has risen because inbound freight, drayage, and customs brokerage are all more expensive. Third, lead-time variability is up, which undermines the EOQ assumption of a predictable lead time and pushes brands toward larger safety stocks.

The practical adjustment is not to abandon EOQ, it is to rerun it. Update annual demand, ordering cost, and holding cost at least once a quarter rather than once a year. On tariff-exposed SKUs, run EOQ two ways, once with current duty and once with a buffered duty rate, so you can see which order size is least sensitive to another tariff move. Pair it with a shorter review of SKU velocity so the demand input does not lag reality.

How can a 3PL help you actually apply EOQ?

EOQ is only as good as its three inputs, and most brands cannot produce clean numbers for all three on their own. A third-party logistics partner fixes the input problem in three ways.

First, on holding cost, a 3PL sees exactly what each unit costs per month in storage, by pallet or cubic foot, including inbound handling. That removes the guesswork around H. Second, on ordering cost, a 3PL can report the inbound processing cost per PO by SKU, which is the hardest piece for a brand to self-report accurately. Third, on demand, a warehouse management system gives you SKU-level velocity data that beats any spreadsheet pulled from Shopify or Amazon Seller Central alone.

Beyond inputs, a 3PL affects the math itself. Multi-node warehousing shortens lead times, which shrinks required safety stock, which means more cash stays out of inventory and in the business. And holding cost per unit typically drops with 3PL volume discounts on pallet storage, which lowers H and makes larger EOQs economic.