What are Defects per Unit?

Defects per unit (DPU) is the number of defects divided by the number of products, and is considered the universal measure of quality. Thus, if there are 50 defects in 1,000 units produced, then the defects per unit will be 0.05.

An essential element in any calculation of defects per unit is what constitutes a defect. Merely changing the definition of a defect can have a profound impact on the reported outcome. For example, if a drilled hole has to be drilled with an accuracy of 1/1000th of an inch, then the DPU may be quite high, at 0.20. However, if some variation is allowable, where the drilling accuracy is acceptable with an accuracy of 1/10th of an inch, then the DPU declines to just 0.001. The latter figure may very well be correct, as long as the resulting variability in the drilled hole is still acceptable within the production process.

Understanding Defects per Unit

DPU is a measure of what is wrong with a process; a high DPU is a strong indicator that a process requires significant corrective action. When variations and defects have been reduced, customer satisfaction is increased, which ultimately results in an improved profit number. Thus, defects per unit are strongly correlated with customer satisfaction and profitability.