defectpercentage

Defect percentage is a measure used in quality control to express the proportion of defective units in a batch, typically shown as a percentage. It is commonly referred to as the defect rate or defect percentage and is used to gauge the quality level of a production lot or process.

The standard calculation is defect percentage = (number of defective units / total number of units) × 100, where a unit is counted as defective if it fails to meet specified requirements. In many contexts, the defect percentage reflects whether a unit has at least one defect, rather than counting the total number of individual defects per unit.

For example, in a batch of 5,000 items with 75 defective units, the defect percentage is (75 / 5,000) × 100 = 1.5%. In some cases, multiple defects per unit may exist, in which case other metrics such as defects per unit or defects per million opportunities (DPMO) may be more informative.

Defect percentage is used for monitoring quality over time, evaluating supplier performance, and guiding process improvements. It has limitations: it does not indicate defect severity or the number of defects per defective unit, and results can be influenced by sampling methods, inspection criteria, and how defects are defined. Related metrics include yield, first-pass yield, and DPMO.