Aftermarket, Field Service & Service Parts worked example

Service Parts Demand at 68% stocking readiness: a worked example

This worked example runs the service parts demand numbers for a tougher week than the baseline: 68% stocking readiness instead of the typical 95%. Estimate service parts demand from installed-base failure events, replacement parts per event, stocking readiness, and usable demand yield.

The inputs for this scenario

  • Parts used per service event: 1.8 parts/event (held at the documented default)
  • Forecast service events: 420 events (held at the documented default)
  • Stocking readiness: 68 % (the input this scenario stresses; the baseline uses 95)
  • Usable demand yield: 92 % (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Gross service parts demand = parts used per service event × forecast service events.
  • Usable service parts demand works out to 473 service parts at these inputs, and this is the headline figure for the scenario.
  • Gross service parts demand works out to 756 service parts at these inputs.
  • Demand missed by stocking readiness works out to 242 service parts at these inputs.
  • Demand lost to forecast yield works out to 41.13 service parts at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where stocking readiness sits at 95% and the headline result is 661 service parts, this scenario comes in 28.42% below the baseline at 473 service parts.
  • Use it to set replenishment quantities and safety stock for a service parts SKU over a forecast period. A result at this level usually justifies acting on the stressed input before touching anything else, because every other figure in the table is downstream of it.

Results at a glance

  • Usable service parts demand: 473 service parts (headline result)
  • Gross service parts demand: 756 service parts
  • Demand missed by stocking readiness: 242 service parts
  • Demand lost to forecast yield: 41.13 service parts

Run it with your numbers

  • To rerun this with your own numbers, open the live Service Parts Demand calculator, set stocking readiness to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.