Sigma levels determine the rate of defects and are a standardized measure of the error rate of a process, based on the Defects per Million Opportunities (DPMO) estimate. The Sigma Level estimate is a long-term estimate of the process defect opportunities. At the Six Sigma level, a business process produces only 3.4 defects per million opportunities.
As the name suggests, Defects per million opportunities (DPMO) is the number of defects in a process per one million opportunities.
Defects per million opportunities is calculated by the number of defects, divided by the number of units times the number of opportunities, multiplied by one million.