Reorder Point Calculator
Find the stock level at which to place your next order, from daily sales, your supplier's lead time and how often you're willing to run out.
From placing an order to the stock arriving.
How much daily demand swings. A rough guess is fine; the standard deviation calculator can work it out from past sales.
Reorder when stock falls to
324 units
- Used during the lead time
- 280 units
- Safety stock
- 44 units
- Days of stock at the reorder point
- 8.1 days
Place a new order when stock falls to 324 units: enough for the 7-day wait plus 44 units of safety stock.
How it's worked out
- Demand during the lead time
40 a day × 7 days280 - Safety stock for 95%
1.6449 × 10 × √743.5 - Reorder point
280 + 43.5, rounded up324
- The service-level safety stock assumes daily demand varies at random and the lead time is steady. If deliveries are often late, keep extra on top.
How it is worked out
Demand during the lead time is daily demand × lead time. Safety stock for a service level is z × the daily standard deviation × √lead time, where z is 1.28 for 90%, 1.64 for 95%, 2.05 for 98% and 2.33 for 99%. The reorder point is the two added together, rounded up.
Questions people ask
What is the reorder point for 40 a day with a 7-day lead time?
280 units covers the wait. With demand that swings by 10 units a day and a 95% service level, add 44 units of safety stock, so reorder at 324.
What is the reorder point formula?
Reorder point = daily demand × lead time in days + safety stock.
What is a service level?
The share of order cycles in which you don't run out. 95% means running out in about 1 cycle in 20; a higher level needs more safety stock.
How do I find the variation in demand?
Take your daily sales for the last few weeks and work out the standard deviation, for example with the standard deviation calculator. A rough guess is better than none.
About this calculator
Formula and rules last checked 10 November 2026Written and tested by the CalculatorDex teamReport a problem