The calculation of a Sigma level, is based on the number of defects per million opportunities (DPMO).

In order to calculate the DPMO, three distinct pieces of information are required:

a) the number of units produced

b) the number of defect opportunities per unit

c) the number of defects

The actual formula is:

DPMO = (Number of Defects X 1,000,000)

((Number of Defect Opportunities/Unit) x Number of Units)

Example:

A manufacturer of computer hard drives wants to measure their Six Sigma level.

Over a given period of time, the manufacturer creates 83,934 hard drives.

The manufacturer performs 8 individual checks to test quality of the drives.

During testing 3,432 are rejected.

Defects 3432 DPMO 5111.158768

Opportunities 83934 Sigma Level 4.1

Defect Opportunities per unit 8

Six Sigma Table: 1 690,000

2 308,000

3 66,800

4 6,210

5 320

6 3.4