Sigma Level Calculator
Find your process sigma level from real defect data — the headline Six Sigma quality figure. Free, instant and fully in your browser, using the standard 1.5σ-shift convention.
Sigma level
3σ
with the conventional 1.5σ shift
The 1.5σ shift is a Motorola convention, not a statistical necessity: it is why 6σ maps to 3.4 DPMO. Some statisticians consider the shift arbitrary.
σ = NORMSINV(1 − DPMO/1,000,000) + 1.5
Raise your sigma level with stable work
You calculated this from estimates. Measure the real one from shop-floor video.
What is process sigma level?
Process sigma level expresses quality as the number of standard deviations between the process mean and the nearest specification limit. Higher is better: a higher sigma level means fewer defects. The Six Sigma convention adds a 1.5σ shift to account for long-term process drift, which is why a Six Sigma process (sigma level 6) corresponds to about 3.4 defects per million opportunities rather than the far smaller figure a pure 6σ tail would suggest.
How to calculate sigma level
- 1
Gather defect data
Record units inspected, opportunities for a defect per unit, and the total defects found.
- 2
Convert to DPMO and yield
DPMO = defects / (units × opportunities) × 1,000,000. Yield is the share with no defects.
- 3
Read your sigma level
Sigma level = the inverse normal of the yield, plus the conventional 1.5σ shift. Use it to benchmark and track the process over time.
Frequently asked questions
Why is the 1.5 sigma shift added?
Short-term capability tends to degrade over the long run as a process drifts. The 1.5σ shift is the standard Six Sigma adjustment for that drift, so the reported sigma level reflects realistic long-term performance — and is why 6σ equals about 3.4 DPMO.
What sigma level should I aim for?
Many processes operate around 3–4 sigma. World-class quality targets six sigma (≈3.4 DPMO). The right target depends on the cost and risk of defects in your specific process.
How does Yamazo Studio support quality improvement?
Yamazo Studio turns shop-floor video into time studies, standard work and waste analysis, helping you stabilise the work so variation — and defects — go down.