Reorder Point Calculator
Enter how many units you sell per day on average and how long your supplier takes to deliver. Add a safety stock, or let the calculator derive one from your busiest days and slowest deliveries. You get the reorder point and a suggested order quantity. Nothing is sent anywhere.
In one sentence: The reorder point is the stock level at which you must place an order so that stock arrives before you run out, including a safety buffer.
Formula: reorder point = average daily sales × average lead time + safety stock; derived safety stock = (max daily sales × max lead time) − (average daily sales × average lead time).
Why a reorder point and not a calendar
Ordering on a fixed day each month ignores the two things that cause stockouts: sales spikes and late deliveries. A reorder point ties the order to actual stock. When units on hand fall to the point, you order, and the stock remaining is what you expect to sell while the supplier's delivery is on its way, plus a buffer. The buffer, safety stock, is what absorbs a busy week or a shipment that arrives late.
Choosing safety stock
The simplest method is to pick a number of units you are comfortable holding as insurance. The derived method is more defensible: it covers the worst realistic case, your busiest daily sales for the longest lead time you have seen, minus the average case you already cover. It can produce a large buffer for products with volatile sales or unreliable suppliers; that is the point, and it is also a prompt to find a steadier supplier. Products that are cheap to hold and painful to run out of deserve more safety stock than expensive, slow sellers.
Order quantity
The suggested quantity simply covers a target number of days at average sales. Match it to your supplier's minimum order, carton sizes and the turnover you want to keep: longer cover means fewer orders but more cash in stock. Review the daily sales figure monthly, since the reorder point drifts as demand changes.
Frequently asked questions
What counts as lead time?
Days from placing the order to the stock being available to sell, including production, shipping, customs and receiving.
Should I include stock already on order?
Yes. Compare the reorder point with units on hand plus units already ordered and not yet received.
Is my data stored?
No. Everything runs in your browser.