Safety stock calculator
Size a stock buffer from average daily demand, demand variability, supplier lead time, and a target service level — then see what each service level costs you in working capital.
- Demand across the lead time
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- Standard deviation over the lead time
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- Safety stock at 95
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- Extra days of cover
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- Total cover before a reorder
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Choose a service level.
How this is calculated: safety stock = z × σ × √(lead time), and the reorder point = average daily demand × lead time + safety stock. The square root appears because daily demand is summed across the lead time, so the variation over that window grows with √days rather than with days. Two honest caveats: the normal distribution is a modelling choice, not a property of the data, and real demand for a small business is often lumpy — a handful of big orders rather than a smooth daily average — which this model does not represent. The demand, variability, and service level are the reader’s own assumptions, so treat the result as a planning model rather than a measured benchmark.
Need the buffer tied to actual stock levels?
NoxOrigin tracks receiving, counts, adjustments, and reorder signals against live stock, so the service level you pick here can be checked against what your stock actually does — instead of standing alone as a spreadsheet number.
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