Reorder Point and Safety Stock Calculator
Enter daily demand, its variability and the lead time.
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Reorder Point and Safety Stock Calculator by TheCalcTools
How the Reorder Point and Safety Stock Calculator works
Reorder when stock falls to the demand expected during the lead time plus a safety buffer. With normally distributed daily demand, safety stock = z × σ × √(lead time), where z sets the service level.
Higher service levels need disproportionately more stock: going from 95% to 99% raises safety stock by about 40%.
The formula
Worked example
Using the default values shown in the calculator:
| Average daily demand (units) | 40 |
|---|---|
| Standard deviation of daily demand | 12 |
| Lead time (days) | 9 |
| Service level (chance of not running out during the lead time) | 95% |
- At 95% service: safety stock 60 units.
- Reorder when stock reaches 420 units.
Result:
| Safety stock (units) | 60 |
|---|---|
| Reorder point (units) | 420 |
| Expected demand during the lead time | 360 |
Frequently asked questions
What if lead time also varies?
Add lead-time variability: SS = z √(L σ_d² + d² σ_L²). This calculator assumes a fixed lead time.
Sources and further reading
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This calculator gives estimates for information only. Check important results independently before you rely on them. See our disclaimer.