Reorder Point Calculator — (Average Daily Sales × Lead Time) + Safety Stock

Order too late and you stock out; order too early and your cash sits in boxes. The reorder point is the stock level that threads the two: when on-hand inventory falls to it, you place the next order, sized so the delivery lands just as you start touching your safety stock. This calculator takes your average daily sales and lead time, and either accepts a safety stock figure you already have — from the safety stock calculator linked below, for example — or computes one on the spot with the simple max-and-average formula.

¿Trabajas en español? La calculadora en español del stock de seguridad obtiene también el punto de reorden con el método estadístico: Calcular Stock de Seguridad — Fórmula y Punto de Reorden.

The formula

Reorder point = (average daily sales × lead time in days) + safety stock. The first term is lead-time demand: what you expect to sell while the order travels. The second is the buffer for when reality is worse than the expectation — a slower delivery or a hotter week. Both terms must use the same units and the same lead time definition: if your supplier quotes 5 working days but the truck arrives on calendar day 7, the honest input is 7.

Worked example

Average sales of 40 units a day and a 6-day lead time give lead-time demand of 240 units. Add a safety stock of 360 units — the figure the simple formula produces for a product whose worst stretch is 10 days at 60 units a day — and the reorder point is 600 units: when the shelf count reaches 600, order. The calculator reproduces this in both modes: type 360 as the safety stock, or switch to the simple-formula mode and enter the max lead time and max daily sales and watch it derive the same 360.

Setting the order quantity is a separate question

The reorder point says when, not how much. Order quantity is its own decision (batch sizes, supplier minimums, price breaks, shelf life), and confusing the two is a classic error: a correct reorder point with a tiny order quantity means reordering constantly; with a huge one, it means the buffer math was pointless. Set the point from this page, then set the quantity from your supplier’s terms and your turnover figures.

When to recalculate

The inputs decay. A promotion, a marketplace listing taking off, a supplier moving warehouses — each changes daily sales or lead time, and a reorder point computed on stale inputs fails quietly: no error message, just a stockout on a Friday. Recompute per product whenever lead time changes, after any sustained change in daily sales (two weeks is a practical trigger), and before seasonal peaks, using the peak’s own sales rate rather than the annual average. Products with erratic demand need the buffer reviewed most often, because the safety stock term is doing the heaviest work there.

A failure you can recognise

Here is how a stale reorder point breaks. A product sells 40 units a day with a 6-day lead time, so the point sits at 600 including buffer. A marketplace feature doubles sales to 80 a day, but nobody recomputes: the point is still 600, which is now just 7.5 days of stock — while the order still takes 6 days to arrive and the buffer was sized for the old pace. The store stocks out two days before the delivery, during its best traffic week of the quarter. Nothing malfunctioned; the formula was simply fed last month’s business. The fix costs two minutes: recompute the point whenever the sales rate moves — after features, promotions, seasonality turns — and let the safety stock term, not hope, absorb what is left of the uncertainty.

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Reorder Point Calculator — When to Reorder, with Safety Stock Built In