Safety Stock Calculator
Estimate a demand-variability buffer for a fixed replenishment lead time.
Example result
Assumes independent daily demand, approximately normal variation and fixed lead time. A z-score of 1.65 approximates a 95% cycle service level, not fill rate.
How to calculate it
Assumes independent daily demand, approximately normal variation and fixed lead time. A z-score of 1.65 approximates a 95% cycle service level, not fill rate.
Worked example
This is an illustrative scenario, not a market benchmark. Select “Reset to example” to reproduce it in the calculator.
- Daily demand standard deviation
- 8 units/day
- Fixed lead time
- 9 days
- Service-level z-score
- 1.65 z
Safety stock rounded up: 40 units
Safety Stock FAQ
What if lead time varies?
This model can understate risk. Measure lead-time variability and use a model that includes both sources of uncertainty.
What does this calculation leave out?
Assumes independent daily demand, approximately normal variation and fixed lead time. A z-score of 1.65 approximates a 95% cycle service level, not fill rate.
Are my inputs saved or sent to a server?
Calculations run in your browser. We do not send your inputs or results to our server or analytics. A comparison stays in this tab until it is refreshed. A CSV is saved only when you choose to download it. See our privacy policy for ordinary hosting and optional analytics data.
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