Free tool · For DTC brands on Shopify

Economic Order Quantity (EOQ) Calculator

Order a huge batch and you tie up cash and warehouse space in stock that sits for months; order tiny batches and you pay the per-order cost — freight minimums, receiving, admin — over and over. The economic order quantity is the sweet spot in between: the order size that makes your total inventory cost as small as possible. Enter your own numbers for one SKU and see it.

Your numbers, for one SKU

Do this per product (or per variant). Everything updates instantly. Nothing is sent anywhere — this runs entirely in your browser.

Annual demand — units of this SKU you sell (or expect to sell) in a year.

units/yr

Cost per purchase order — the fixed cost of placing one order, no matter its size: freight minimum, PO admin, receiving/QC labor.

Unit cost (what you pay) — your landed cost per unit from the supplier, not the retail price.

Annual holding-cost rate — your estimate: yearly cost of holding a unit as a % of its value (capital, storage, insurance, shrinkage, obsolescence). ~20–30% is commonly cited for DTC — adjust to your business.

%/yr

Your current order size — units you typically order per PO right now. Optional — used only to show how much you'd save by switching to the EOQ. Enter 0 to skip.

units

Your order quantity

Economic order quantity

Order this often

—

Annual ordering cost orders per year × cost per order	$0
Annual holding cost average stock (half the order size) × holding cost per unit	$0
= Total annual inventory cost at the EOQ — the lowest it can be	$0
Orders per year how many POs you'd place for this SKU	0
Days between orders	—

Read this as a planning estimate, not a guarantee. It uses the standard EOQ (Wilson) formula — EOQ = √(2 × annual demand × cost per order ÷ annual holding cost per unit), where holding cost per unit = unit cost × holding-cost rate. At the EOQ your annual ordering cost and annual holding cost are equal — that balance is exactly what makes the total the smallest it can be. The classic model assumes steady demand, a fixed per-order cost, and no supplier price breaks for bulk; if your supplier gives volume discounts or has hard MOQs, treat the EOQ as a starting point and round to a practical order size. Every number here comes only from the values you typed.

How to read it

Economic order quantity — order roughly this many units each time you restock this SKU to keep ordering + holding cost as low as possible.
The two costs balance — order bigger than the EOQ and holding cost climbs faster than ordering cost falls; order smaller and the reverse. At the EOQ they're equal, so the total is at its minimum.
It's a flat-bottomed curve — being 20–30% off the EOQ barely changes the total cost, so round to a sensible, ship-friendly quantity (a full pallet, a carton multiple). Don't chase the exact decimal.

Why the right order size still leaks money silently

The EOQ is only as good as the annual demand you feed it — and that number comes straight from your sales and inventory data. In practice that data quietly drifts: a 3PL or ERP sync half-fails, a bundle decrements the wrong SKU, returns never restock, so the units-sold and on-hand figures in Shopify stop matching reality. Plan your order size off a demand number that's silently wrong and you over-order slow movers (dead stock, obsolescence write-offs) or under-order your heroes (stockouts and oversell). Nothing errors; you just find out from a warehouse full of the wrong stock.

How Ops Monitor keeps the inputs honest

Ops Monitor connects to your Shopify (and 3PL/ERP) with read-only API keys and watches your inventory and sync continuously — flagging count drift, negative or impossible on-hand levels, stalled syncs, and oversell risk, and alerting you by email or Slack the moment the numbers stop matching reality. That way the demand and stock figures you plan order quantities from can actually be trusted.

It is read-only: it never writes to your store and never changes stock or places orders. It detects and alerts — it does not reorder for you or guarantee stock levels. One avoided dead-stock write-off or hero-SKU stockout is usually worth far more than the $149/month price.

See for yourself

Start watching your inventory counts in minutes with read-only keys — $149/month, self-serve, cancel anytime.

Start monitoring — $149/mo →

Not ready? Run the free, no-signup Ops Scorecard to see where your store is most exposed. Or have us hand-check one messy SKU/sync for you with the $29 one-time ops audit.