Inventory how-to

How to adjust reorder points when sales change

Reorder points should move whenever your daily sales rate moves.

Short answer: Reorder points should move whenever your daily sales rate moves. The formula is daily sales x (lead time + safety days), so if daily sales go up or down, the reorder point goes up or down with it. Check this regularly rather than setting it once and forgetting it.

Why reorder points go stale

A reorder point set during a slow month will be too low once sales pick up, and you will stock out before the new order arrives. A reorder point set during a peak will be too high once sales slow down, and you will tie up cash in stock that sits on the shelf. The fix is to recalculate on a schedule, not just when something goes wrong.

What drives the change

Three things feed the formula: daily sales rate, supplier lead time, and safety days. Daily sales is the number that moves most often, usually because of seasonality, a promotion, a new listing going live, or a product losing popularity. Lead time and safety days change less often, but you should still check them after a supplier changes their process or after a shipping delay.

How often to review

Review reorder points at least monthly for most SKUs. Review weekly for fast movers or anything on promotion, since a few days of inflated sales can shift the daily rate a lot. Review less often for slow movers where a short-term blip does not change the picture much.

Step by step

  1. Pull recent sales for the SKU over a consistent window, such as the last 28 days.
  2. Recalculate the daily sales rate from that window.
  3. Confirm lead time and safety days are still accurate for that supplier.
  4. Recalculate reorder point as daily sales x (lead time + safety days).
  5. Compare the new reorder point to the old one and update it if the gap is meaningful.
  6. Flag SKUs with sudden sales spikes or drops for a manual check, since a short window can overreact to a one-off event.
  7. Repeat on a fixed schedule so changes do not build up unnoticed.

Worked example

Suppose a SKU sold at 4 units a day last month, with a 14-day lead time and 5 safety days, giving a reorder point of 4 x (14 + 5) = 76 units. This month a promotion pushes daily sales to 10 units a day. The reorder point should become 10 x (14 + 5) = 190 units. If you leave the reorder point at 76, you will trigger a reorder far too late and run out of stock before the new shipment lands.

How SteadyShelf helps

SteadyShelf recalculates the daily sales rate from a rolling 28-day window by default, so reorder points adjust automatically as sales rise or fall, and it factors in each supplier's lead time and safety days. It does not do per-location forecasting, so if sales shift differently across locations you will still need to judge that split yourself.

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

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FAQ

Should I manually override the reorder point during a known sales spike, like a holiday?

Yes, if you know the spike is coming before the sales data reflects it. Raise the reorder point ahead of time based on your own estimate, then let the recalculated daily rate take over once real sales data comes in from the event.

What if sales are too erratic to get a stable daily rate?

Use a longer averaging window to smooth out the noise, and lean on safety days a bit more to cover the uncertainty. For very low-volume SKUs, a rolling average over several months is usually more useful than a short recent window.

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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