Statistical Safety Stock and Reorder Point Calculator
Size a normal-demand safety-stock scenario for fixed lead time and a selected one-sided cycle-service target.
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Result
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Calculation steps
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How to calculate
Scale independent per-period demand variation by the square root of fixed lead time, multiply by the service z factor and add average lead-time demand.
σlead=σperiod√L; safety=zσlead; reorder point=mean demand×L+safety
Worked example
Mean 100 units/day, SD 20 units/day and fixed lead time 4 days give lead-time mean 400 and SD 40. At 95% one-sided cycle service, reorder point≈465.794, rounded to 466 units.
Assumptions and input details
Independent stationary demand increments, fixed lead time and an approximate normal lead-time demand distribution. Lead time must match the demand period unit. Fractional periods assume variance scales proportionally with time. A cycle-service target is the probability of no stockout during a replenishment cycle, not unit fill rate. Demand correlation, variable lead time, ordering calendars, lost sales and parameter-estimation uncertainty are excluded. This sizes safety stock separately from EOQ cost optimization.
References: Oracle: safety stock and reorder point calculations
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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