The Six Sigma Handbook, Revised and Expanded, 2nd Edition

Appendix 18. Process σ Levels and Equivalent PPM Quality Levels

Based on the assumption that in the long term the process could drift by plus or minus 1.5σ.

Process σ Level	Process PPM
6.27	1
6.12	2
6.0	3.4
5.97	4
5.91	5
5.88	6
5.84	7
5.82	8
5.78	9
5.77	10
5.61	20
5.51	30
5.44	40
5.39	50
5.35	60
5.31	70
5.27	80
5.25	90
5.22	100
5.04	200
4.93	300
4.85	400
4.79	500
4.74	600
4.69	700
4.66	800
4.62	900
4.59	1,000
4.38	2,000
4.25	3,000
4.15	4,000
4.08	5,000
4.01	6,000
3.96	7,000
3.91	8,000
3.87	9,000
3.83	10,000
3.55	20,000
3.38	30,000
3.25	40,000
3.14	50,000
3.05	60,000
2.98	70,000
2.91	80,000
2.84	90,000
2.78	100,000
2.34	200,000
2.02	300,000
1.75	400,000
1.50	500,000