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Lot Rejection Rate, PPM and Sigma Level Calculator

Supplier scorecards live on three numbers: how many lots you reject, how many parts per million are bad, and what that means in sigma terms. This calculator turns raw counts from SAP QM usage decisions into all three.

Your numbers

Lots inspected

lots

Lots rejected

lots

Units received

units

Defective units found

units

Defect opportunities per unit

Number of independent ways a unit can be defective.

Your results

Lot rejection rate

2.5%

PPM defective

1,500

Lot acceptance rate

97.5%

DPMO

375

Unit yield

99.9%

Sigma level (with 1.5 shift)

4.8706

Sigma level uses the conventional 1.5 sigma long-term shift. Quote the method when reporting to customers.

Save results:

Sigma level vs defective units found

Sweeps Defective units found from 10 to 1000, holding your other inputs fixed.

Vendor quality dashboard from SAP

Optional: ask how to get PPM and lot rejection trends from SAP QM without manual exports.

Optional. The tool and every export work without this. No spam.

How to use it

Enter lots inspected and lots rejected for the period, the units received and the defective units found, and the number of defect opportunities per unit. PPM measures defective units, while DPMO measures individual defects per opportunity, so the opportunities field only affects DPMO and sigma. Use one opportunity per unit if you want a simple pass or fail view.

Formulas

Lot rejection rate = rejected lots / inspected lots. PPM = defective units / units received x 1,000,000. DPMO = defects / (units x opportunities) x 1,000,000. Sigma level = normsinv(1 - DPMO/1,000,000) + 1.5, where the 1.5 is the Motorola long-term shift convention. Three sigma is roughly 66,800 DPMO and six sigma 3.4 DPMO.

Where the counts come from

In SAP QM, inspection lots end with a usage decision (QA11), and the quality score and lot statistics sit in the vendor evaluation and the QM information system. Make sure your counts match one definition of rejection: lots with a rejected usage decision, or lots with blocked stock posted, since they can differ when conditional acceptance is used.

Common mistakes

Counting lots accepted on deviation as good without saying so, comparing PPM across suppliers with different sampling plans, and calculating PPM from sample defects without scaling to the lot. Where only samples are inspected, PPM from samples estimates but does not measure lot quality.

Frequently Asked Questions

What is the difference between PPM and DPMO?

PPM counts defective units per million units. DPMO counts defects per million opportunities, so a unit with two defects counts twice and the number of ways to fail is part of the denominator.

Why add 1.5 to the sigma level?

It is a convention that allows for long-term drift of the mean. Without the shift, the same DPMO would give a sigma level 1.5 lower.

What is a good supplier PPM?

It depends on the industry and part. Automotive customers often target double digit PPM, while commodity items may accept hundreds. Set targets in the quality agreement.

Can I use sample defects?

Only if the sample is random and you scale it up. Otherwise the result describes the sample, not the lot population.

We can calculate vendor PPM and rejection trends from SAP QM data on demand and highlight the vendors drifting, using your own system.

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