S&OP, Demand Planning & Forecasting worked example

Forecast Bias at 65% plan attainment: a worked example

This worked example runs the forecast bias numbers for a tougher week than the baseline: 65% plan attainment instead of the typical 90%. Estimate forecast bias for sandop, demand planning and forecasting using production-ready inputs so teams can confirm whether capacity can cover demand before committing the schedule.

The inputs for this scenario

  • Net forecast error per planning cycle: 4 units / cycle (held at the documented default)
  • Planning cycles in the review window: 480 cycles (held at the documented default)
  • Plan attainment (uptime equivalent): 65 % (the input this scenario stresses; the baseline uses 90)
  • Forecast-to-actual pass rate: 97 % (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Gross forecast bias capacity = forecast bias output per cycle × available forecast bias cycles.
  • Good forecast bias capacity works out to 1,211 units at these inputs, and this is the headline figure for the scenario.
  • Gross forecast bias capacity works out to 1,920 units at these inputs.
  • Forecast bias downtime loss works out to 672 units at these inputs.
  • Forecast bias yield loss works out to 37.44 units at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where plan attainment sits at 90% and the headline result is 1,676 units, this scenario comes in 27.78% below the baseline at 1,211 units.
  • Use it when you need to convert a recurring per-cycle forecast bias into a total unit impact over a planning horizon. 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

  • Good forecast bias capacity: 1,211 units (headline result)
  • Gross forecast bias capacity: 1,920 units
  • Forecast bias downtime loss: 672 units
  • Forecast bias yield loss: 37.44 units

Run it with your numbers

  • To rerun this with your own numbers, open the live Forecast Bias calculator, set plan attainment to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.