How to prevent stockouts in a Shopify store: a weekly routine

Most stockouts aren't surprises. The warning was there weeks earlier: stock covered fewer days than the supplier needed to deliver. The fix is to look at the right number, early enough, every week.

Why stockouts happen

• Ordering too late: the reorder decision was made against stock on hand instead of lead time.
• Under-estimated demand: averages dragged down by days the product was already out of stock.
• Supplier delays: planning with the quoted lead time instead of the real one.
• No buffer: no safety stock, so any spike or late delivery empties the shelf.

The early-warning number: days of cover vs lead time

Days of cover = units on hand ÷ daily sales

Compare it with the supplier's lead time plus the days of safety stock you want. If days of cover is lower, you're already late.

Example: 90 units on hand, selling 6 a day, gives 15 days of cover. The supplier takes 21 days. Even ordering today, expect about 6 days without stock unless you expedite, split the order or slow sales.

Include units already on order: (on hand + incoming) ÷ daily sales tells you whether the order you placed last month is enough.

A 20-minute weekly routine

1. List products whose stock position is at or below their reorder point (see the reorder point guide). Order these first.
2. List products that will reach it within 7 days. Order these this week if the supplier has a minimum order or ships weekly.
3. Check open purchase orders against expected arrival dates. If a supplier is late, re-plan the affected products with the real lead time.
4. Look for demand changes. A product selling 50% faster than last month needs a new reorder point now, not next quarter.
5. Glance at excess stock. Cash tied up in slow movers is cash you can't spend on best sellers.

Size the buffer to what a stockout costs

Best sellers and products that drive repeat orders deserve a higher service level (98–99%); slow, cheap-to-miss items can run at 90%. The safety stock guide shows the math.

When you're already out

• Order immediately and ask the supplier for a partial early shipment.
• Consider showing a restock date on the product page rather than hiding it, if your theme supports it.
• After it's back, don't let the out-of-stock days drag down its forecast. Exclude them.

Doing this by hand works for a few dozen products. Reorder Radar runs the same checks across your whole catalog every day and ranks what needs attention: see the live demo.