10 Warning Signs You're About to Run Out of Stock
Ten warning signs a Shopify SKU is about to run out of stock — before the low-stock badge shows up and a customer tells you first, not the report.
By the time a Shopify product shows "Out of stock," the actual warning happened days or weeks earlier. Something in your sales data, your operations, or your supplier relationship already told you this was coming — you just weren't looking at the right number yet.
This list is the fast version: ten places to check, grouped by where the signal actually shows up first. For the slower, process version — comparing days of inventory against lead time on a schedule — see how to predict a stockout before it happens. If you're past spotting individual signals and want the full prevention picture, start there instead.
Sales signals
These show up in your own sales numbers, before anything on the shelf looks unusual.
- Days of inventory is falling toward your lead time, not away from it. If days of inventory for a SKU keeps shrinking relative to how long your supplier takes to deliver, the gap that protects you is closing — even if the raw stock count still looks fine at a glance.
- Average daily sales moved and the reorder point didn't. A reorder point set on last quarter's velocity is already wrong once this quarter's velocity is higher — the alert fires too late for the pace you're actually selling at now.
- A promotion, feature, or seasonal push is drawing a SKU down faster than its normal pace assumed. A spike is exactly what a safety-stock buffer exists for, but only if you notice it's happening while there's still time to react.
Operational signals
These live in Shopify itself, in the gap between what the numbers say and what's actually true.
- Available and On hand have started to disagree. A growing gap between what Shopify says you can sell and what's physically on the shelf hides the real countdown to zero behind a number that isn't tracking reality. Closing that gap fixes it — watching for it just tells you it's happening.
- A SKU has sat in "Committed" longer than your usual fulfillment window. Stock tied up in unfulfilled orders isn't available for anyone else to buy, and a growing backlog here quietly eats into what looks like remaining stock.
- Nobody has recalculated this SKU's reorder point since its last sales spike. A number that was right in June and never touched again isn't protecting the store that exists now — it's protecting the one that existed when someone last did the math.
Supplier signals
These come from outside your store, and they're the easiest to miss because nothing in Shopify flags them on its own.
- Your supplier's last shipment landed later than the lead time you're still planning around. If the real lead time has quietly grown, every reorder point calculated on the old number is already set too low.
- A purchase order you expected to ship hasn't been confirmed. Silence a few days past when you'd normally hear back is worth a check-in before it becomes a missed delivery window.
- Your supplier's minimum order quantity or price changed and nobody adjusted the order size. A higher MOQ can mean the quantity you'd normally reorder no longer clears the minimum, which delays placing the order at all, not just the shipment.
- A second SKU from the same supplier is showing the same pattern. One SKU running low might be that SKU's problem. Two or three from the same supplier at once is usually the supplier's problem.
Checking all ten of these by hand across a real catalog — every SKU, every supplier, every week — is the part that quietly stops happening once you're past a few dozen products. StockCue tracks days of inventory against lead time for every SKU it watches and sends a "Reorder soon" alert seven days before you actually cross the reorder point, ahead of most of the signs above.
STOCKCUE
Ten signals is a lot to track by hand across a growing catalog. StockCue checks every tracked SKU against its reorder point and flags it a week before you'd actually run out — in-app alerts on the Free plan, email alerts from Starter up.
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Devmerx is a Shopify and WordPress development agency helping DTC brands build faster stores, cleaner migrations, and higher-converting experiences. Based in London, UK, serving clients worldwide.
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