NPI, DFM/DFA & Engineering Change worked example

Prototype Build Cost at 92% build yield: a worked example

Push build yield up to 92% and the picture changes. This example computes every intermediate figure at that operating point. A design engineer budgeting a prototype run to validate a new part ahead of committing to production tooling.

The inputs for this scenario

  • Prototype Units Built: 25 units (unchanged)
  • Cost Per Prototype Unit: 320 $/unit (unchanged)
  • Build Yield: 92 % (raised for this scenario; the documented default is 80)
  • Soft Tooling & Setup: 6,500 $ (unchanged)

Working through the calculation

  • Applying the documented formula (Prototype build cost = prototype units x cost per unit x build yield% + soft tooling setup) to the inputs above produces each figure below.
  • At this operating point the engine returns 13,860 $ for total prototype build cost, the number this scenario is built around.
  • At this operating point the engine returns 554 $ / piece for prototype build cost per unit.
  • At this operating point the engine returns 7,360 $ for variable prototype build cost.
  • At this operating point the engine returns 6,500 $ for fixed prototype build cost adder.

How this compares with the baseline

  • Against the tool's baseline example, where build yield sits at 80% and the headline result is 12,900 $, this scenario comes in 7.44% above the baseline at 13,860 $.
  • It combines variable build cost (units x per-unit cost x yield) with fixed soft tooling to produce total prototype build cost and cost per usable unit. The value of this scenario is the size of the gap it exposes: that gap, priced out over a year, is the budget you can justify spending to close it.

Results at a glance

  • Total prototype build cost: 13,860 $ (headline result)
  • Prototype build cost per unit: 554 $ / piece
  • Variable prototype build cost: 7,360 $
  • Fixed prototype build cost adder: 6,500 $

Run it with your numbers

  • Every input above is editable in the live Prototype Build Cost calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.