How to use the defect PPM and yield calculator
Once a defect rate drops below a tenth of a percent, percentages stop communicating anything useful, which is why manufacturing plants quote parts per million instead. Enter total units produced, defects found, and opportunities per unit, and this calculator returns defect rate, PPM, yield, DPMO, and an estimated sigma level.
Use DPMO rather than PPM whenever a single unit carries many inspected features. Comparing a twenty-component assembly against a single-feature part on a straight PPM basis unfairly penalizes the harder process. Leave opportunities per unit at 1 and PPM and DPMO come out identical.
The sigma level converts DPMO into normal-distribution margin and includes the conventional 1.5 sigma long-term shift, so the familiar benchmarks below apply.
| Sigma level | DPMO | Yield |
|---|---|---|
| 3.0 | 66,807 | 93.32% |
| 4.0 | 6,210 | 99.38% |
| 5.0 | 233 | 99.977% |
| 6.0 | 3.4 | 99.99966% |
Final-inspection yield flatters a long process. Rolled throughput yield multiplies every step together, so collecting PPM at each operation is what exposes where the money is actually leaking.
Frequently asked questions
PPM counts rejected units per million units produced, while DPMO counts defects per million inspection opportunities. When one unit has many inspected features, DPMO reflects process difficulty far more fairly.
It is the conventional long-term shift allowance used in Six Sigma work, assuming the process mean drifts about 1.5 sigma over time. With that shift, six sigma corresponds to 3.4 DPMO.
Rolled throughput yield multiplies every step together, so ten steps at 99% each end up near 90% overall. Track yield step by step rather than only at final inspection.