Quality & Metrology worked example

Defects Per Unit with total defects found during inspection of 9 defects: a worked example

Here is what the math looks like when conditions slip. We hold every other input steady and drop total defects found during inspection to 9 defects, then walk the calculation through step by step. Calculate defects per unit (DPU) by dividing the number of defects found by the number of units inspected.

The inputs for this scenario

  • Total defects found during inspection: 9 defects (the input this scenario stresses; the baseline uses 18)
  • Units inspected in the sample: 400 units (held at the documented default)
  • Reporting conversion factor (e.g. per 100): 1 x (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Defects per unit = defects found ÷ units inspected.
  • Defects per unit works out to 0.02 defects / unit at these inputs, and this is the headline figure for the scenario.
  • Raw ratio works out to 0.02 value at these inputs.
  • Conversion factor works out to 1 x at these inputs.
  • Units inspected works out to 400 value at these inputs.

How this compares with the baseline

  • Against the tool's baseline example, where total defects found during inspection sits at 18 defects and the headline result is 0.05 defects / unit, this scenario comes in 50% below the baseline at 0.02 defects / unit.
  • The practical read: the gap between this scenario and the baseline is entirely attributable to total defects found during inspection, so recovering it is worth quantifying in dollars before considering equipment or staffing changes. DPU counts defects, not defective units, so a high DPU can come from a few heavily flawed units or many lightly flawed ones — it does not tell you the defective-unit rate by itself.

Results at a glance

  • Defects per unit: 0.02 defects / unit (headline result)
  • Raw ratio: 0.02 value
  • Conversion factor: 1 x
  • Units inspected: 400 value

Run it with your numbers

  • To rerun this with your own numbers, open the live Defects Per Unit calculator, set total defects found during inspection to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.