What Is Economic Order Quantity (EOQ)? Formula, Examples & Limits

Economic order quantity (EOQ) is the mathematically optimal number of units to order at one time — the quantity that minimizes the combined cost of ordering inventory and holding it. Order too little too often, and your ordering costs pile up. Order too much at once, and you're paying to store inventory that sits idle. EOQ finds the exact midpoint where those two costs are lowest together.

It's a formula from 1913 that still shows up in every inventory management textbook — and for good reason. Even if you never calculate it precisely, understanding EOQ changes how you think about reordering.

The EOQ Formula (And What Each Variable Actually Means)

The standard EOQ formula is:

EOQ = √(2DS / H)

Where:

• D = Annual demand (total units sold per year)
• S = Ordering cost per order (cost to place and receive one purchase order)
• H = Holding cost per unit per year (warehousing, insurance, opportunity cost, spoilage)

Let's be specific about what these variables include, because vague definitions are where most EOQ calculations go wrong.

D (Annual Demand): Pull this from your sales data. If you sold 1,200 units last year, D = 1,200. If demand is seasonal, you'll want to think about whether a yearly average actually represents your business — more on that later.

S (Ordering Cost): This is the cost to place one purchase order — not the cost of the goods themselves. It includes your time spent creating and sending the PO, supplier communication, receiving and inspecting the shipment, and any fixed shipping fees. For a small DTC brand, this might be $15–$50 per order. For a larger operation with formal procurement, it can be $100+.

H (Holding Cost): This one trips people up. It's not just rent. Holding cost includes:

• Warehouse space (your cost per square foot × space per unit)
• Insurance on inventory
• Shrinkage and spoilage rates
• The opportunity cost of capital tied up in stock (typically 20–30% of unit cost annually is a reasonable estimate)

If your unit cost is $10 and you use 25% as your holding cost rate, H = $2.50 per unit per year.

EOQ Worked Example for an Ecommerce Store

Let's run through a concrete example.

You sell a skincare product on Shopify. Here's what you know:

• Annual sales: 2,400 units (D = 2,400)
• Cost to place and receive one order: $30 (S = 30)
• Unit cost: $12, holding cost rate: 25%, so H = $3.00

Plug into the formula:

EOQ = √(2 × 2,400 × 30 / 3)
EOQ = √(144,000 / 3)
EOQ = √48,000
EOQ = ~219 units

So your optimal order quantity is about 219 units. At 2,400 units per year, that means you'd place roughly 11 orders per year — or about one every 33 days.

Now here's where it gets useful: if your supplier MOQ is 500 units, you immediately know you're probably over-stocking relative to the EOQ ideal. That's a signal to negotiate MOQs, look for alternate suppliers, or recalculate whether the volume discount justifies the higher holding cost.

What EOQ Is Actually Minimizing

The total inventory cost curve has two components moving in opposite directions:

• Ordering costs decrease as you order larger quantities (fewer orders per year)
• Holding costs increase as you order larger quantities (more inventory sitting)

EOQ is the point where those two lines cross — total cost is at its minimum. If you graph it, it looks like a U-shaped curve with the bottom at your EOQ quantity.

The practical insight: small deviations from the EOQ don't dramatically increase your costs. The curve is relatively flat near the bottom. If EOQ says 219 units but your supplier sells in cases of 240, ordering 240 won't ruin your margins. The formula gives you a target, not a rigid rule.

How to Find Your Ordering Cost and Holding Cost

These two inputs are where most people either guess wildly or give up on EOQ entirely. Here's a simple way to estimate them for a Shopify store:

Ordering cost (S):
Track the time your team spends per purchase order — emailing the supplier, following up, receiving the shipment, doing a stock count, entering it in your system. Multiply by hourly labor cost. Add any fixed freight or customs brokerage fees. Even a rough figure ($20–$60 for most small brands) is better than leaving it blank.

Holding cost (H):
Start with 25–30% of unit cost as your annual holding cost rate if you don't have precise warehouse data. It's a widely-used approximation. If you have actual warehouse costs, divide your annual storage expense by average units stored to get a more accurate per-unit figure.

When Economic Order Quantity Breaks Down (And Ecommerce Is Full of These Cases)

EOQ was designed for a world of stable, predictable demand and constant costs. Ecommerce doesn't always play nicely with those assumptions.

Seasonal demand: EOQ uses annual average demand. But if you sell 80% of your units in Q4, ordering a fixed EOQ quantity every 33 days makes no sense. You'd need to segment the formula by season — or switch to a demand-driven reorder approach entirely.

Supplier MOQs and price breaks: Most suppliers offer volume discounts or have minimum order quantities that ignore your EOQ completely. When there's a 10% discount at 500 units and your EOQ is 219, you need to compare the total cost at both quantities (including the discount savings) rather than blindly following the formula.

Variable lead times: EOQ tells you how much to order but not when to order. For that, you need a reorder point calculation — and if your supplier's lead time varies from 2 to 6 weeks, that uncertainty needs to be covered by safety stock, not EOQ.

New products: EOQ requires historical demand data. For a product you just launched, you're estimating D, which makes the formula less reliable. Use it as a starting point, but revisit it after 90 days of actual sales data.

EOQ and Reorder Points: How They Work Together

EOQ answers "how much to order." Reorder point answers "when to order." You need both.

Your reorder point is typically:

ROP = (Average daily sales × Lead time in days) + Safety stock

If you sell 7 units/day and your supplier takes 14 days to deliver, your reorder point is 98 units (plus whatever safety stock you want as a buffer). When your stock hits 98, you place an order for your EOQ quantity.

This is where a tool like Alertr fits in practically — it tracks your sell rate and current stock levels, and alerts you when you're approaching your reorder point, so you don't have to manually watch every SKU every day. For stores managing 100–500 SKUs, that kind of automated monitoring is what makes EOQ actually usable in practice, rather than a spreadsheet exercise you do once and forget.

A Quick EOQ Calculator Table for Common Scenarios

Here are pre-calculated EOQ ranges for common ecommerce situations, assuming S = $30 and H = 25% of unit cost:

Annual Units Sold	Unit Cost	EOQ (approx.)	Orders per Year
600	$10	120	5
1,200	$10	170	7
2,400	$10	240	10
600	$30	69	9
1,200	$30	98	12
2,400	$30	138	17

Notice that as unit cost increases, EOQ drops — because the holding cost per unit is higher, so you want to carry less at a time. Higher-cost products should generally be ordered in smaller, more frequent batches.

The Real Value of EOQ (Even When You Don't Use It Precisely)

Even if you never plug exact numbers into the EOQ formula, the concept changes how you evaluate your current ordering behavior in concrete ways:

• If you're ordering in huge bulk to "save on shipping," EOQ helps you quantify whether the freight savings actually outweigh your holding costs.
• If you're placing tiny orders every week because you're nervous about overstock, EOQ might show that slightly larger, less frequent orders would save you significant time and ordering overhead.
• If a supplier pushes you toward a larger MOQ, EOQ gives you a rational basis for negotiating or walking away.

The formula is a thinking tool as much as a calculation tool.

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If you want to put EOQ into practice without living in spreadsheets, Alertr gives you the sell rate tracking and reorder alerts that make it actually operational — especially if you're managing more than a handful of SKUs. The free tier covers up to 50 SKUs, and the Pro plan is currently in beta at $19/month (locked in for life).

Try Alertr free at getalertr.com