How to Set the Right Low-Stock Threshold for Every Product in Your Shopify Store

If you've set a single “alert me when stock hits 5 units” rule for your entire catalog, you've probably already been burned by it — either a bestseller sold out before the alert gave you time to react, or a slow mover sat at “low stock” for months without ever actually running out. A flat threshold feels simple, but it quietly fails almost every product it's supposed to protect. Getting a proper shopify low stock alert threshold in place means treating it as a per-product calculation, not a store-wide setting.

Why “Low Stock at 5 Units” Doesn't Work for Your Whole Catalog

A single threshold assumes every product behaves the same way. In reality, your catalog is full of products with wildly different sales speeds, supplier relationships, and price points — and a rule built for one breaks for the rest.

Consider what a flat “5 units” threshold actually means for two different products:

• A bestseller selling 20 units a day blows past 5 units in a matter of hours. By the time the alert fires, you may already be out of stock — the warning arrives too late to do anything useful.
• A slow-moving product selling 1 unit a month sits at “low stock” for weeks, training you to ignore the alert entirely. When every alert looks the same, you stop trusting any of them.

Both outcomes defeat the purpose of having alerts at all. The first misses the window to reorder. The second creates so much noise that real warnings get lost in it. A useful threshold has to reflect how fast a specific product actually moves — not a number that felt reasonable when you set it once and forgot about it.

The Factors That Should Actually Set Your Threshold

Instead of one number for everything, base each product's threshold on a handful of factors that genuinely differ across your catalog.

Sales Velocity

This is the single biggest driver. A product that sells 10 units a day needs a much higher unit threshold than one that sells 1 unit a week — not because it's more “important,” but because it burns through inventory faster and needs more runway to react.

Supplier Lead Time

If your supplier can restock in 3 days, you don't need much buffer. If it takes 6 weeks to get a container across an ocean, your threshold needs to account for weeks of sales, not days. Lead time is often the most overlooked factor — merchants set thresholds based on how the product sells, but forget how long it takes to actually fix a shortage once the alert fires.

Seasonality

A product's velocity isn't constant. A swimwear line that sells slowly in October and rapidly in June needs a threshold that flexes with the season, or at minimum, a manual review before your peak period starts. Applying a January threshold to a June sales rate guarantees you'll get blindsided.

Price Point and Margin

High-margin, high-ticket items usually justify a more conservative (higher) threshold, since a single missed sale is expensive and customers researching a big purchase are less likely to wait around for a restock. Lower-margin, low-price items can tolerate a tighter threshold since the cost of an occasional stockout is smaller relative to the effort of managing tighter inventory buffers on every SKU.

A Simple Formula You Can Use

You don't need an inventory science degree to get a reasonable number. This formula gets you most of the way there:

Threshold = (Average Daily Sales × Supplier Lead Time in Days) + Safety Buffer

• Average Daily Sales — pull your last 30-60 days of sales for the product and divide by the number of days. Use a shorter, more recent window for seasonal products.
• Supplier Lead Time — how many days it actually takes from placing a reorder to having stock available to sell, not just the shipping time — include your own processing and receiving delays.
• Safety Buffer — an extra cushion (commonly 20-50% of the calculated amount) to absorb demand spikes, supplier delays, or the time it takes you to notice the alert and act on it.

The result is a threshold that gives you enough runway to reorder before you actually run out — not a round number that happens to look tidy.

Example: Three Products, Three Different Thresholds

Here's how the formula plays out across products with different profiles:

• Bestselling t-shirt — sells 15 units/day, 5-day supplier lead time, moderate buffer. Threshold = (15 × 5) + 25% ≈ 95 units. High velocity demands a high unit threshold, even though it looks like a lot of stock sitting on the shelf.
• Mid-tier accessory — sells 3 units/day, 10-day lead time, standard buffer. Threshold = (3 × 10) + 30% ≈ 40 units. Slower sales, but a longer lead time still requires meaningful runway.
• Niche/slow-moving item — sells 0.3 units/day, 14-day lead time, smaller buffer. Threshold = (0.3 × 14) + 20% ≈ 5 units. Low velocity means a low threshold is genuinely appropriate here — this is the one product where “alert at 5” was actually right all along.

Notice that the three thresholds span nearly a 20x range. That's the whole point: a single store-wide number can only ever be correct for one of these products, and wrong for the other two.

Where Stock Alert Fits In

Calculating and updating a threshold like this for every SKU by hand doesn't scale past a handful of products. Stock Alert lets you set a sensible global default for your store, then override it per product, per collection, or per tag — so your bestsellers get an early warning while slow movers don't clutter your alerts, all through real-time email and Slack notifications the moment any of those thresholds are crossed.

Set It Once, Trust It Every Time

The goal of a low-stock threshold isn't to pick a number that looks safe — it's to give yourself enough time to act before a product actually runs out. That time window is different for every product in your catalog, which means your thresholds should be too.

Start with your top 10-20 bestsellers, run them through the formula above, and set thresholds that reflect how each one actually sells. You'll spend a little more time up front, but you'll end up with alerts you can actually trust — instead of ones you've learned to ignore.