Inventory how-to

How to set low stock alerts that actually work

A low stock alert only works if it fires early enough to let you reorder and receive stock before you sell out.

Short answer: A low stock alert only works if it fires early enough to let you reorder and receive stock before you sell out. That means basing the alert on your lead time and sales rate per variant, not on one fixed number for every product.

Why a flat threshold fails

If you set "alert me at 10 units" for every SKU, you will get alerts too late for fast movers and too early for slow ones. A product that sells 5 units a day needs a much higher threshold than one that sells 5 units a month, because both need to cover the same supplier lead time.

Use a reorder point, not a round number

The right alert threshold is your reorder point: daily sales multiplied by lead time plus safety days. This tells you the stock level at which you need to place an order today to avoid running out before the next delivery arrives.

Base daily sales on recent, real data

Use a recent sales window, not last year's average or a guess. A 28 to 35 day window usually reflects current demand better than a longer one, unless the product is strongly seasonal, in which case you need more history to see the pattern.

Build in safety days for supplier variability

Suppliers do not always ship on time. Add a few safety days to your lead time to cover delays, so the alert fires a bit earlier than the bare minimum math would suggest.

Step by step

  1. List each SKU with its supplier and that supplier's lead time in days.
  2. Calculate average daily sales per variant using a recent window, like the last 28 days.
  3. Add safety days to the lead time to cover supplier delays.
  4. Multiply daily sales by (lead time plus safety days) to get the reorder point for each SKU.
  5. Set your alert or reminder to trigger when stock on hand reaches that reorder point, not a flat number.
  6. Recalculate reorder points periodically, since daily sales change as products trend up or down.
  7. Check alerts against what is already on order, so you do not double up on stock you have already bought.

Worked example

A store sells a candle at 4 units a day on average over the last 28 days. The supplier's lead time is 10 days, and the owner adds 3 safety days for delays. Reorder point = 4 x (10 + 3) = 52 units. So the alert should fire when stock on hand drops to 52 units, not at a flat number like 10 or 20.

How SteadyShelf helps

SteadyShelf does this calculation automatically per SKU, using each supplier's lead time and safety days plus a 28-day sales window, and gives you an order-by date instead of a generic low stock badge. It does not do per-location alerts or forecasts, so if you stock multiple warehouses you will need to track that split manually.

$29/month flat, unlimited products and suppliers, 30-day free trial. Run the numbers now with the free reorder point calculator.

SteadyShelf is launching on the Shopify App Store. Join early access to get the install link first.

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FAQ

Should the sales window be longer for slow-moving products?

Yes. A 28-day window on a product that sells once a week can be skewed by a single order. Widen the window or look at a longer trend for slow movers so you are not reacting to noise.

What if a supplier's lead time changes often?

Update the lead time you use in the calculation as soon as you notice a change, and keep the safety days a bit higher for suppliers with unpredictable shipping. Stale lead time data is one of the most common reasons alerts fire too late.

Let SteadyShelf do this math for every SKU

Order-by dates per supplier, seasonal forecasts and draft POs for your Shopify store. $29/month after a 30-day free trial.

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