Calculation method
First, the tool adds the sellable target, replacement reserve, and non-sale copies. It then divides that post-defect requirement by one minus your defect allowance and rounds up if requested.
Why reserves are separate
Defect allowance protects the production yield. Replacement reserve is held after production for customer service. Non-sale copies are planned uses, not defects; keeping them separate avoids double-counting.
Example
For a 3,000-copy sellable target, a 2% defect allowance, a 1% replacement reserve, and review/demo copies all increase the production run for different reasons.
Limits
These are your planning assumptions, not a predicted defect rate. Confirm factory MOQ, rounding, QA process, and actual reserve policy before placing an order.