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Shopify inventory alert threshold: how to pick the number

Checked against the live sources below on 27 October 2026.

Set the alert at your reorder point: the units you expect to sell while a reorder is on its way, plus safety stock for surprises. Daily sales times lead time, plus a buffer. The safety stock calculator turns your sales variation and supplier delays into the buffer.

The formula

Reorder point = average daily sales × lead time in days + safety stock. Wikipedia’s safety stock article gives the same structure: the reorder point is the level that triggers an order, lead time is the delay before renewed availability, and the buffer depends on the service level you want.

If you only reorder on set days, add the days between orders to your lead time, because a product can run out during that wait too.

An example with made-up numbers

Say a product sells 12 units a day and your supplier takes 14 days. Expected sales during the wait are 12 × 14 = 168 units. If you want a five-day buffer, add 12 × 5 = 60 units. The threshold is 228. When stock reaches 228, an alert should fire. These numbers are only an illustration; use your own.

Two ways to size the buffer

A fixed number of days. Simple, and good enough for steady sellers.
A service level. Safety stock rises with sales variation, supplier lateness, and how rarely you accept a stockout. The safety stock calculator uses the standard formula and shows the result for 90, 95, 98 and 99 percent.

For the service-level method, Wikipedia gives safety stock as the service-level z-score times the square root of (average lead time × demand variance + average demand squared × lead time variance), with z of about 1.64 for a 95% service level. With invented numbers: demand averages 20 a day with a standard deviation of 6, and lead time averages 10 days with a standard deviation of 2. Safety stock is 1.64 × √(10 × 36 + 400 × 4), about 73 units, so the threshold is 20 × 10 + 73 = 273.

Give fast sellers and slow suppliers bigger buffers, and slow sellers smaller ones. One store-wide number rarely fits both.

Where the alert comes from

Once you have the number, enter it in a tool that emails you. On Low Stock Alerts & Notify Me, the Free plan uses one threshold for the store and Pro adds per-product thresholds, according to its listing. Review your numbers each quarter, since sales and lead times drift.

Then check that the alert is working: compare its date with the day you ran short last time, and adjust the number if the email would have come too late or too early.

Turn your sales variation and lead time into a safety buffer.

Safety stock calculator Low Stock Alerts & Notify Me

Frequently asked questions

What is a good low-stock threshold for Shopify?

There is no universal number. It is your daily sales times your supplier lead time, plus safety stock, so it differs for every product.

Should every product share one threshold?

Only if your products sell at similar speeds with similar lead times. Otherwise per-product thresholds are more accurate.

How often should I change it?

Whenever sales speed or supplier lead time changes, and at least once a quarter.

How this page was researched

Read on 27 October 2026. The formula structure comes from the Wikipedia safety stock article; the example is arithmetic on invented numbers; plan details come from our live listing.

Wikipedia: Safety stock — the reorder point is the inventory level that triggers an order; lead time is the delay between reaching it and renewed availability; service level is the desired probability of meeting demand during lead time without a stockout, and a higher service level needs more safety stock
Low Stock Alerts & Notify Me on the Shopify App Store — low-stock email alerts the moment any product or variant drops to your threshold, one alert per dip with no repeats, re-armed when you restock; a notify-me button on sold-out pages that emails waiting shoppers on restock; the Free plan covers low-stock alerts and the back-in-stock button; Pro adds per-product thresholds, Slack and CSV

Disclosure. Low Stock Alerts & Notify Me is our app (Stelar Digital LLC). This page was written with AI tooling and checked against the sources listed above.