Supply Chain & Procurement worked example

Days of Supply with current inventory on hand of 2,300 units: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop current inventory on hand to 2,300 units, then walk the calculation through step by step. Calculate days of supply from inventory, daily usage, and policy factor.

The inputs for this scenario

  • Current inventory on hand: 2,300 units (the input this scenario stresses; the baseline uses 4,500)
  • Average daily demand: 300 units / day (held at the documented default)
  • Coverage safety factor: 1.2 x (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Protected days = inventory on hand ÷ daily usage ÷ safety multiplier.
  • Protected days of supply works out to 6.39 days at these inputs, and this is the headline figure for the scenario.
  • Unprotected days works out to 7.67 days at these inputs.
  • Inventory works out to 2,300 pieces at these inputs.
  • Daily usage works out to 300 pieces / day at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where current inventory on hand sits at 4,500 units and the headline result is 12.5 days, this scenario comes in 48.89% below the baseline at 6.39 days.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to current inventory on hand, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It assumes a flat, constant daily usage rate, so for seasonal or lumpy demand the protected days can mislead — average usage hides the peaks that actually cause stockouts.

Results at a glance

  • Protected days of supply: 6.39 days (headline result)
  • Unprotected days: 7.67 days
  • Inventory: 2,300 pieces
  • Daily usage: 300 pieces / day

Run it with your numbers

  • To rerun this with your own numbers, open the live Days of Supply calculator, set current inventory on hand to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.