# How to convert DPMO/Sigma to Cpk

Six Sigma – iSixSigma Forums Old Forums General How to convert DPMO/Sigma to Cpk

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• #32487

Logan Luo
Participant

Does anyone know how to convert DPMO/Sigma to Cpk?

Thanks

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#86818

SixSigma Sally
Member

Logan-
Cpk = Z(short-term) which is sigma level  /  3
However, if you are starting with DPMO, convert it to a decimal value(divide by 1,000,000), look this decimal value up in a standard normal curve(z table) and find the corresponding z. Minitab can do this as well. Anyway this is long term z. To convert to short term z which is sigma level:
z(short term) which is sigma level = Z(long term) + 1.5
then you can plug into the equation above to get Cpk
Hope this helps.

0
#86837

Logan Luo
Participant

That is exactly the answer I was looking for. Now I can close the loop of my calculator.
In stead of looking Z value in a table, I designed this gadget which is similar to the one in this website to calculate the DPMO, Z value, Yield tp and Cpk for me .

Thanks

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