NPI, DFM/DFA & Engineering Change worked example

Prototype Build Cost at 58% build yield: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop build yield to 58%, then walk the calculation through step by step. Estimate the cost of a prototype build run including per-unit material and labor plus the one-time soft tooling to produce them.

The inputs for this scenario

  • Prototype Units Built: 25 units (held at the documented default)
  • Cost Per Prototype Unit: 320 $/unit (held at the documented default)
  • Build Yield: 58 % (the input this scenario stresses; the baseline uses 80)
  • Soft Tooling & Setup: 6,500 $ (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Prototype build cost = prototype units x cost per unit x build yield% + soft tooling setup.
  • Total prototype build cost works out to 11,140 $ at these inputs, and this is the headline figure for the scenario.
  • Prototype build cost per unit works out to 446 $ / piece at these inputs.
  • Variable prototype build cost works out to 4,640 $ at these inputs.
  • Fixed prototype build cost adder works out to 6,500 $ at these inputs.

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 13.64% below the baseline at 11,140 $.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to build yield, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It applies a single flat yield to the whole build; staged builds where yield improves run to run are better modeled in separate rounds.

Results at a glance

  • Total prototype build cost: 11,140 $ (headline result)
  • Prototype build cost per unit: 446 $ / piece
  • Variable prototype build cost: 4,640 $
  • Fixed prototype build cost adder: 6,500 $

Run it with your numbers

  • To rerun this with your own numbers, open the live Prototype Build Cost calculator, set build yield to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.