Rekenbox · 2026
Safety stock and reorder point
Choose a buffer you understand. See how much stock you need and when to reorder.How your result is built
Demand + buffer = reorder point
The buffer is added to expected demand during 7 days of lead time.
- Expected lead-time demand (units)
- 140
- Inventory position minus reorder point (units)
- -40
- Lead time (days)
- 7
Findings and points to check
- Your inventory position is at or below the reorder point. Check open orders and decide the order quantity; this tool does not place an order.
Assumptions, sources and version
2026 · nl-2026.1 · v2026.1
- Inventory position = on hand + on order − outstanding demand. The reorder point is a reorder trigger, not an order quantity. Use the same day basis for demand and lead time.
- Buffer days are your policy choice and do not provide a calculated service guarantee. The statistical method uses z × daily standard deviation × √lead time: fixed lead time, independent daily demand and a normal approximation. It does not model seasonality, trends or uncertain lead times.
- Cycle service level is the model probability of no stockout during a replenishment cycle; it is not the percentage of items supplied immediately. Stock and reorder points are rounded up to whole units.
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Understand your result
How this tool works
The reorder point combines expected demand during lead time with safety stock. Use buffer days as a practical policy, or the statistical method when you know the standard deviation of daily demand. Inventory position means on hand plus on order minus backorders. A signal does not determine an optimal order quantity.
Common questions
What does service level mean?
In the statistical method it is the probability of no stockout during a replenishment cycle under the model assumptions. It is not the share of orders fulfilled immediately.
Does it handle variable lead times?
The statistical method assumes fixed lead time, independent daily demand and a normal approximation. Variable lead times or strong seasonality need a more detailed model.
Which details do you need?
- How do you want to set your buffer?
- Average demand (units per day)
- Lead time (days)
- Extra buffer days
- Standard deviation of daily demand (units)
- Chosen cycle service level
- Inventory position (units)
Limits of this tool
- Inventory position = on hand + on order − outstanding demand. The reorder point is a reorder trigger, not an order quantity. Use the same day basis for demand and lead time.
- Buffer days are your policy choice and do not provide a calculated service guarantee. The statistical method uses z × daily standard deviation × √lead time: fixed lead time, independent daily demand and a normal approximation. It does not model seasonality, trends or uncertain lead times.
- Cycle service level is the model probability of no stockout during a replenishment cycle; it is not the percentage of items supplied immediately. Stock and reorder points are rounded up to whole units.
Year: 2026 · Version 2026.1
Sources for this tool
- MIT OpenCourseWare — stochastic-demand inventory models · calculation source checked 2026-09-06
Prepared by the Rekenbox product team at Winstwaker. The listed source references and calculation version make the method traceable. Report a content error Last updated: 2026-09-06. Rekenbox is a product by Winstwaker. The tool applies a calculation model to your inputs; a result or paid report is not a personal assessment by an adviser.