The stock level at which to place your next order, with every step shown.
Reorder point (units)
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Enter the average usage and the lead time to see the reorder point.
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Enter your average usage and your supplier’s lead time, add a safety stock, and the calculator gives your reorder point: the stock level at which to place an order so that it arrives before you run out. Add the stock on hand and anything already on order to see whether it is time to reorder, or how long you have. It also offers a cautious maximum usage method, based on maximum usage and maximum lead time, with the minimum (buffer), maximum and average stock levels.
Day, week or month: usage, lead times and safety cover are all counted in this unit. If you sell seven days a week but your supplier quotes working days, convert the lead time to calendar days: an order placed on a working day with a 10-working-day lead time arrives 14 days later, or more when a bank holiday falls in between.
Take average usage from past sales: 900 units sold in 30 days is 30 units a day. Lead time runs from placing the order to having the goods ready to sell, including receiving and checking them. Give the safety stock in units, or as time of usage, such as 3 days of average sales.
The reorder point is rounded up to a whole unit, so rounding never eats into the safety stock; the other quantities are exact. The time until the reorder point is rounded down to a tenth. Copy the workings, export them as a CSV file or save them to Priostack.
Usage during lead time = average usage × average lead time.
Reorder point = usage during lead time + safety stock.
Maximum usage method: reorder level = maximum usage × maximum lead time; safety stock (buffer, or minimum level) = reorder level − average usage × average lead time; maximum stock level = reorder level + order quantity − minimum usage × minimum lead time.
Average stock = safety stock + order quantity ÷ 2.
It is time to reorder when stock on hand plus stock on order is at or below the reorder point.
This is ACCA’s example: with demand of 30 units a day and a lead time of 5 days, usage during the lead time is 30 × 5 = 150 units, which is the reorder point with no safety stock. Add a safety stock of 3 days of sales, 30 × 3 = 90 units, and the reorder point rises to 150 + 90 = 240 units. With 300 units on the shelf and nothing on order, you will need to reorder in (300 − 240) ÷ 30 = 2 days.
Multiply average usage by the lead time, in the same time unit, then add the safety stock. At 12.5 units a day, a 7-day lead time and 3 days of safety stock: 12.5 × 7 = 87.5, plus 12.5 × 3 = 37.5, gives a reorder point of 125 units.
It sets the reorder level at maximum usage × maximum lead time, so stock lasts until the delivery as long as usage and lead time stay within the highest you have seen. The buffer, or minimum level, is the reorder level less average usage × average lead time, which is how ACCA defines buffer inventory. With one order open at a time, stock peaks when usage is lowest and delivery fastest: reorder level + order quantity − minimum usage × minimum lead time. With usage of 200 to 600 units a week (400 on average), a lead time of 4 to 6 weeks (5 on average) and orders of 4,000 units, the reorder level is 3,600 units, the buffer 1,600 and the maximum level 6,800.
Safety stock is the reserve that covers a rise in sales or a late delivery; you should only dip into it now and then. The reorder point is higher: it is the safety stock plus what you use during the lead time. ACCA calls safety stock buffer inventory, the amount by which the reorder level exceeds average demand in the lead time.
There is no official rule. Too little and you run out; too much and cash sits on the shelf. A simple choice is the gap between the worst case (maximum usage × maximum lead time) and average usage during the average lead time, which is what the maximum usage method gives. ACCA describes two finer approaches: weighing the cost of holding stock against the cost of running out, or choosing a service level, an acceptably small chance of running out.
Use the same unit as your usage. If you sell every day, convert to calendar days: in England and Wales, an order placed on Monday 14 December 2026 with a 10-working-day lead time arrives on Wednesday 30 December, 16 days later, because Christmas Day and the Boxing Day substitute holiday on Monday 28 December fall in between. Bank holidays differ by nation: in 2026 there are 8 in England and Wales, 10 in Northern Ireland, and 10 in Scotland, including a one-off holiday on 15 June.
Yes. Compare the reorder point with stock on hand plus anything ordered but not yet received. Otherwise, while a delivery is on its way your stock looks too low and you would order twice. This matters most when your order quantity is less than usage during the lead time, as several orders are then open at once.
This calculator gives general information, not legal, tax, financial or accounting advice. The result is only as good as the figures you enter: check your real lead times and sales before setting reorder levels.
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