Aftermarket, Field Service & Service Parts worked example

Service Parts Forecast Accuracy at 63% target forecast accuracy: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop target forecast accuracy to 63%, then walk the calculation through step by step. Calculate forecast accuracy for service parts from correctly forecast demand, actual demand, and an accuracy target.

The inputs for this scenario

  • Correctly forecast service part demand: 1,120 parts (held at the documented default)
  • Actual service part demand: 1,280 parts (held at the documented default)
  • Target forecast accuracy: 63 % (the input this scenario stresses; the baseline uses 88)

Working through the calculation

  • The calculation starts from the formula this tool documents: Forecast accuracy = correctly forecast demand ÷ actual service part demand × 100.
  • Service parts forecast accuracy works out to 87.5 % forecast accuracy at these inputs, and this is the headline figure for the scenario.
  • Forecast accuracy gap works out to -24.5 percentage points at these inputs.
  • Correctly forecast demand works out to 1,120 parts at these inputs.
  • Actual service part demand works out to 1,280 parts at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where target forecast accuracy sits at 88% and the headline result is 87.5 % forecast accuracy, this scenario lands almost exactly on the baseline at 87.5 % forecast accuracy.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to target forecast accuracy, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It scores only the parts you forecast correctly against actuals and does not separate over-forecast from under-forecast bias, so a high score can still hide directional planning errors.

Results at a glance

  • Service parts forecast accuracy: 87.5 % forecast accuracy (headline result)
  • Forecast accuracy gap: -24.5 percentage points
  • Correctly forecast demand: 1,120 parts
  • Actual service part demand: 1,280 parts

Run it with your numbers

  • To rerun this with your own numbers, open the live Service Parts Forecast Accuracy calculator, set target forecast accuracy to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.