Machine Vision & Industrial Inspection AI worked example

False Reject Cost at 1.8% false reject rate: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop false reject rate to 1.8%, then walk the calculation through step by step. Estimate the monthly cost of false rejects from a machine vision or automated inspection system, where good parts are incorrectly flagged as defective and removed from production.

The inputs for this scenario

  • Monthly production volume inspected: 50,000 parts / month (held at the documented default)
  • Cost per falsely rejected good part: 4.8 $ / part (held at the documented default)
  • False reject rate (good parts wrongly rejected): 1.8 % (the input this scenario stresses; the baseline uses 2.5)
  • Fixed monthly sorting and containment cost: 800 $ (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Monthly false rejects = monthly production volume x false reject rate / 100.
  • Total monthly false reject cost works out to 5,120 $ at these inputs, and this is the headline figure for the scenario.
  • False reject cost per inspected part works out to 0.1 $ / piece at these inputs.
  • Variable false reject cost works out to 4,320 $ at these inputs.
  • Fixed sorting and containment cost works out to 800 $ at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where false reject rate sits at 2.5% and the headline result is 6,800 $, this scenario comes in 24.71% below the baseline at 5,120 $.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to false reject rate, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. It counts only false rejects of good parts; it does not value missed defects (false accepts) or downstream escape costs.

Results at a glance

  • Total monthly false reject cost: 5,120 $ (headline result)
  • False reject cost per inspected part: 0.1 $ / piece
  • Variable false reject cost: 4,320 $
  • Fixed sorting and containment cost: 800 $

Run it with your numbers

  • To rerun this with your own numbers, open the live False Reject Cost calculator, set false reject rate to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.