THE FEUTEX TOOLKIT

Demand-Variability Safety Stock

Estimate a buffer from independent daily demand variation and fixed replenishment lead time.

Supply Chain workspace● Runs in your browser

01 Your input

Daily sigmaitems/dayLead daysdaysZstandard deviationsUnit costcurrency

02 Your result

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Result data

Formula

Safety units = Math.ceil(v.z*v.daily_sigma*Math.sqrt(v.lead_days)) ; Buffer value = Math.ceil(v.z*v.daily_sigma*Math.sqrt(v.lead_days))*v.unit_cost

Sources and model references

https://learning.sap.com/courses/mastering-sap-ibp-for-inventory-planning-and-optimization-br/exposure-demand-supply-variability-and-service-variability-calculations-1

Worked example

Inputs

Daily sigma: 12 items/day
Lead days: 9 days
Z: 1.645 standard deviations
Unit cost: 20 currency

Expected results

Safety units: 60 items
Buffer value: 1200 currency

Load the example in the workspace to reproduce these results. Display rounding does not change the underlying calculation.

How to use this tool

Enter your own assumptions using a consistent currency and period.
Review the scenario outputs and compare alternative inputs.
Check the stated model limits before using the result in an operating plan.

Try this example

{
  "daily_sigma": 12,
  "lead_days": 9,
  "z": 1.645,
  "unit_cost": 20
}

Accuracy and scope

Normal approximation with independent daily demand and fixed lead time. User supplies z; no service-level guarantee or lead-time variability is modeled.

Is my data uploaded?

This tool runs locally in your browser. Input and output are not sent to a processing server. Copy or download your result before leaving the page.