Safety Stock Calculator
Work out safety stock from demand variation and lead time.
Runs in your browser. Nothing is uploaded — your input is processed on this device and discarded when you close the tab.
Safety Stock Calculator
How to use this tool
- Enter the service factor Z for your target service level.
- Enter the standard deviation of daily demand.
- Enter the lead time in days and press Generate.
Worked example
With a service factor of 1.65, demand variation of 20 units and lead time of 4 days, safety stock is 1.65 x 20 x square root of 4 = 1.65 x 20 x 2 = 66 units.
What this tool does not do / Limits
This is a planning estimate only. It assumes demand follows a normal pattern and lead time is fixed, and it ignores supplier reliability, seasonality and order-size rules.
Frequently asked questions
What Z value should I use?
Common values are 1.28 for 90%, 1.65 for 95% and 2.33 for 99% service levels.
Should I round the result?
Yes, round up to whole units, since you cannot hold a fraction of most items.
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