Quality worked example

Defect Rate with defects found of 9 defects: a worked example

This worked example runs the defect rate numbers for a tougher week than the baseline: defects found of 9 defects instead of the typical 18 defects. Calculate defect percentage, PPM, and defects per million opportunities.

The inputs for this scenario

  • Defects found: 9 defects (the input this scenario stresses; the baseline uses 18)
  • Units inspected: 5,000 units (held at the documented default)
  • Defect opportunities per unit: 4 opp / unit (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Defect rate = defects รท units inspected.
  • Defects PPM works out to 1,800 PPM at these inputs, and this is the headline figure for the scenario.
  • Defect rate works out to 0.18 % at these inputs.
  • DPMO works out to 450 DPMO at these inputs.
  • Quality rate works out to 99.82 % at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where defects found sits at 18 defects and the headline result is 3,600 PPM, this scenario comes in 50% below the baseline at 1,800 PPM.
  • Use it when reporting line or supplier quality on a scorecard, converting an internal reject count into a customer-facing PPM number, or estimating sigma level from a defect opportunity model. 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

  • Defects PPM: 1,800 PPM (headline result)
  • Defect rate: 0.18 %
  • DPMO: 450 DPMO
  • Quality rate: 99.82 %

Run it with your numbers

  • To rerun this with your own numbers, open the live Defect Rate calculator, set defects found to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.