DPMO and Sigma Level Calculator
DPMO puts different products and processes on one scale by counting defects against the number of ways each unit could fail. This calculator converts raw counts into DPMO, yield and a sigma level you can put on a Six Sigma project dashboard.
Your numbers
Count only opportunities that are really inspected and could fail independently.
All defects, including several on one unit.
Your results
Sigma level depends heavily on how opportunities are defined. Compare only processes that count opportunities the same way.
Sigma level vs defects found
Sweeps Total defects found from 1 to 400, holding your other inputs fixed.
Defect metrics from ERP quality data
Optional: share how defects are recorded in your ERP and we can outline an automated DPMO report.
Optional. The tool and every export work without this. No spam.
How to use the calculator
Enter the units inspected, the number of defect opportunities on each unit and the total defects found. The tool computes DPMO, defects per unit, a Poisson first pass yield estimate and the sigma level. Choose whether to add the conventional 1.5 sigma shift that most published sigma tables include. Use the chart to see how the sigma level would change if the defect count were higher or lower on the same volume.
- Defects can exceed defective units, so count every defect.
- Keep the opportunity definition fixed between before and after measurements.
- Use the same inspection method each period.
Formulas
DPO is defects divided by units times opportunities. DPMO is DPO times one million. DPU is defects divided by units, and first pass yield is estimated by e raised to minus DPU. The sigma level is the inverse normal of (1 minus DPO) plus the shift. With the 1.5 shift, 3.4 DPMO is 6.0 sigma, 233 DPMO is 5.0, 6,210 is 4.0, 66,807 is 3.0 and 308,538 is 2.0. Without the shift each of those values drops by 1.5.
Worked example
A PCB assembly line inspects 5,000 boards with 8 inspected opportunities each, 40,000 opportunities in all, and finds 62 defects. DPO is 0.00155, so DPMO is 1,550. DPU is 0.0124, giving a first pass yield of about 98.8 percent. The normal inverse of 0.99845 is about 2.96, so with the shift the sigma level is about 4.46. Cutting defects to 20 would raise it to roughly 4.9.
Common mistakes
The biggest abuse is inflating the number of opportunities to make sigma look better. Count only characteristics that are actually checked and can fail independently. Another is mixing attribute data from different inspection stages, and a third is quoting a sigma level without saying whether the 1.5 shift was used. For continuous data, use capability indices instead of DPMO whenever you have measurements.
Frequently Asked Questions
What is a good DPMO?
Six Sigma is 3.4 DPMO with the 1.5 shift, but most manufacturing processes run between 4 and 5 sigma, roughly 233 to 6,210 DPMO. A good target depends on the cost of the defect and what your customers require.
Why add the 1.5 sigma shift?
It is a convention from Motorola that allows for long-term drift of the process mean. Many tables and training materials use it. It is empirical and debated, so state clearly which convention you use and stay consistent.
How do I count opportunities?
Count each distinct characteristic that is inspected and could be wrong independently, such as each solder joint class or each dimension on the drawing. Do not count items that cannot fail or that are inspected with no pass-fail criteria.
Can I use this for services or transactions?
Yes. Units can be invoices, orders or calls, and opportunities can be fields or steps that can be wrong. The same formulas apply, as long as defects and opportunities are defined clearly and counted consistently.
If your defect counts are scattered across ERP quality notifications and inspection lots, we can help you build a private report that tracks DPMO by line, part and period.
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