How to set a low-stock threshold you can actually trust

Why one number for the whole catalogue fails

Set the threshold at 10 for everything and you get two failures at once. Your fast seller hits 10 on a Friday afternoon and is gone by Saturday, long before the restock lands — the alert was useless. Meanwhile your slow seller sits at 9 for four months, alerting you about a problem that will not arrive until spring.

The number that matters is not how many units are left. It is how many days of selling are left, measured against how long a restock takes.

The arithmetic

Three inputs, one number:

• Daily sales — how many units of this product you sell on an average day.
• Lead time — the days between deciding to reorder and having stock on the shelf, including your supplier's turnaround and your own admin.
• Buffer — a few extra days for the week the product goes unexpectedly well, or the supplier is slow.

A worked example

Say you sell a house coffee blend. You move about 6 bags a day. Your roaster needs 5 working days, and getting the order placed realistically takes you another 2. So your true lead time is 7 days, and you want 3 days of buffer.

6 a day × (7 + 3) days = 60. Your threshold for that product is 60 bags, not 10. An alert at 10 would reach you roughly eight days too late — which is exactly why the old threshold felt useless.

Now run the same sum for a product you sell one of every other day, with the same supplier: 0.5 × 10 = 5. Same store, same supplier, thresholds of 60 and 5. That is the point.

Where to put the numbers

In WooCommerce, the store-wide default lives under WooCommerce → Settings → Products → Inventory, and each product's Inventory tab can override it. Set the store-wide number for the long tail, then do the arithmetic properly for your top sellers — the twenty or so products that make most of your revenue. Those are the ones where being out of stock actually costs you.

In Steadel you set a threshold per store and adjust as you learn, and alerts go to email or Slack.

Revisit it when the season turns

Sales velocity is not fixed. A product that moved 6 a day in October may move 20 a day in December, and a threshold calculated in the quiet season will fire far too late in the busy one. Recheck your top sellers before any period you expect to be busy.

The honest test is simple: when an alert arrives, could you still have reordered in time? If the answer is no more than once, the number is too low, not the tool.