Planning worked example

Safety Stock with average daily demand of 450 units / day: a worked example

Push average daily demand up to 450 units / day and the picture changes. This example computes every intermediate figure at that operating point. Use when setting inventory buffers for purchased or manufactured parts with variable demand.

The inputs for this scenario

  • Average daily demand: 450 units / day (raised for this scenario; the documented default is 180)
  • Daily demand standard deviation: 36 units (unchanged)
  • Lead time: 12 days (unchanged)
  • Service factor: 1.65 z (unchanged)

Working through the calculation

  • Applying the documented formula (Safety stock = service factor × demand standard deviation × √lead time) to the inputs above produces each figure below.
  • At this operating point the engine returns 206 units for safety stock, the number this scenario is built around.
  • At this operating point the engine returns 5,400 units for lead-time demand.
  • At this operating point the engine returns 5,606 units for protected quantity.
  • At this operating point the engine returns 0.46 days for buffer days.

How this compares with the baseline

  • Against the tool's baseline example, where average daily demand sits at 180 units / day and the headline result is 206 units, this scenario lands almost exactly on the baseline at 206 units.
  • It computes the units of buffer stock needed to hit a chosen service level given daily demand variability over the replenishment lead time. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Safety stock: 206 units (headline result)
  • Lead-time demand: 5,400 units
  • Protected quantity: 5,606 units
  • Buffer days: 0.46 days

Run it with your numbers

  • Every input above is editable in the live Safety Stock calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.