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Shopify’s “days of inventory remaining” estimate tells you how long current stock may last at a recent sales rate. It does not, by itself, tell you when to place a replenishment order. For reorder timing, account for demand during supplier lead time and add safety stock: reorder point = average daily sales × supplier lead time + safety stock.
Why days of inventory remaining is not a reorder date
Shopify’s Inventory remaining per product report estimates stock duration by dividing ending quantity by average units sold per day. Its sales-rate window is the previous 28 days. A variant with no sales in the selected period shows N/A because Shopify lacks enough information for that calculation; a negative ending quantity is displayed as zero days. Shopify documents the report and its calculation here.
That result is a velocity-based estimate, not a supplier-aware trigger. If you have 20 days of cover but replenishment takes 25 days, waiting until the estimate reaches zero is too late. Conversely, a low days-remaining figure does not automatically mean an order is needed if a shipment is already on its way.
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Calculate a reorder point that includes lead time
Shopify’s inventory guidance gives a practical starting formula:
Reorder point = average daily sales × supplier lead time + safety stock
Use the same units throughout: if average sales are measured per day, express lead time in days and safety stock in units. For example, at 4 units sold per day, a 14-day supplier lead time, and 20 units of safety stock, the trigger is 76 units: (4 × 14) + 20. When available inventory reaches that level, the policy says to place a replenishment order. This is an illustrative calculation, not a recommended buffer for every store.
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Shopify defines safety stock as surplus inventory held to protect against demand variability or supply delays. The right amount depends on the uncertainty your business needs to absorb; the formula does not determine that buffer for you.
Use actual supplier performance, not just the promise
Track how long deliveries actually take and update your lead-time assumption when performance changes. Shopify’s inventory reporting guidance illustrates the risk with a supplier that promises 14 days but regularly takes 21. If your planning uses only the promised duration, the reorder point may trigger too late.
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Compare cover with the replenishment horizon
Think of days of cover as a warning indicator, then compare it with the time stock must last: supplier lead time plus whatever buffer your policy requires. The report answers “How long might this stock last at the recent rate?” The reorder point answers “At what stock level should I act so replenishment can arrive before I run short?”
Check the inputs before trusting the trigger
A reorder point is only useful when its underlying inventory and demand data are credible. Review these inputs together:
- On-hand stock: Verify counts and reconcile discrepancies before making a decision based on a low-stock warning.
- Sales velocity: Use a rate suited to the product and planning period. Shopify’s 28-day calculation is a documented historical measure, not a guarantee that the period captures promotions, seasonality, or sudden changes.
- Supplier lead time: Record actual delivery intervals and revise the planning figure when they drift.
- Safety stock: Set a deliberate buffer for the demand or supply variability you need to cover.
- Incoming stock and open purchase orders: Account for confirmed replenishment so you do not order as though no stock is on the way. Shopify’s inventory reporting guide includes incoming inventory in restock planning.
- Location: Check where units are held and whether a transfer can meet demand. Shopify says location-level days remaining can help identify which location may run out first and inform location-specific reorders or transfers; see its analytics data reference.
When receiving a shipment, Shopify’s reporting guidance recommends checking scanned quantities against the open purchase order and assigning stock to the correct location before making it available. That helps prevent an inaccurate receipt from distorting later reorder decisions.
Use sales history as a forecast input, not a guarantee
Shopify says order forecasting uses historical sales data to predict future demand and can inform inventory levels, seasonal planning, and the effects of promotions on order volume. Its Help Center says stores with some sales history can begin planning with eight weeks of consistent weekly orders. That is a starting point, not a promise that every product has enough history for a reliable forecast. Read Shopify’s order forecasting guidance.
Best Value
For context across online and in-store activity, Shopify says its inventory reports consolidate forecasting data in one admin and show daily sales quantities, sell-through rates, and channel-level performance. Those views can add useful context, but they do not replace checking lead time, buffer stock, and incoming orders.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When an inventory app may help
Shopify notes that merchants may use inventory apps for capabilities beyond default reports, including low-stock alerts, reorder thresholds, and purchase-order recommendations. These can make a defined policy easier to operate, but a feature listing is not evidence that an app’s forecast is accurate.
Before choosing a tool, check whether it explains its calculation and whether it accounts for supplier lead times, safety stock, incoming stock and purchase orders, multiple locations, and products with little or no sales history. Also check whether it can provide alerts or purchase-order recommendations in a way that fits your workflow. For example, the Shopify App Store listing for Stockie describes forecasting, lead-time and safety-stock settings, purchase orders, receiving, and low-stock alerts; those are listing claims, not independently verified performance results.
What to do when the report shows N/A or zero days
N/A for a product with no sales in the period
N/A means the report cannot calculate inventory days from sales in the selected period. It is not proof that demand is zero or that stock is safe. Use other relevant sales history or a deliberate planning assumption, and review the product’s stock and supplier timing before setting a trigger.
Zero days with a negative ending quantity
Shopify displays negative ending quantity as zero days. Treat that as a signal to reconcile inventory records and investigate whether the product is already oversold or otherwise unavailable, rather than reading it as a precise forecast of when stock will run out.
Quick Recap
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