Planning worked example
Safety Stock with average daily demand of 90 units / day: a worked example
Suppose average daily demand falls to 90 units / day. This page works the full calculation at that level so you can see exactly which result moves and by how much. Estimate buffer stock from demand variation, lead time, and a service factor.
The inputs for this scenario
- Average daily demand: 90 units / day (the input this scenario stresses; the baseline uses 180)
- Daily demand standard deviation: 36 units (held at the documented default)
- Lead time: 12 days (held at the documented default)
- Service factor: 1.65 z (held at the documented default)
Working through the calculation
- The calculation starts from the formula this tool documents: Safety stock = service factor × demand standard deviation × √lead time.
- Safety stock works out to 206 units at these inputs, and this is the headline figure for the scenario.
- Lead-time demand works out to 1,080 units at these inputs.
- Protected quantity works out to 1,286 units at these inputs.
- Buffer days works out to 2.29 days at these inputs.
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. When the numbers land here, the stressed input is the lever to work; the walkthrough above shows exactly how much each output recovers as it climbs back toward the baseline.
Results at a glance
- Safety stock: 206 units (headline result)
- Lead-time demand: 1,080 units
- Protected quantity: 1,286 units
- Buffer days: 2.29 days
Run it with your numbers
- To rerun this with your own numbers, open the live Safety Stock calculator, set average daily demand to your actual value, and adjust the remaining inputs to match your operation.
Last reviewed 2026-05-12.