Definition DPPM - Defective Parts Per Million Calculation Formula

There are no dumb questions, right? Some people need to see this in writing. Calculation for DPPM is "one million divided by the units shipped then multiply by the parts found defective", Right? My cohort in crime has made me "brain dead" on this. Thanks.

I had to write it down, but if you do the math its the same...I just always reversed the order.. defects divided by # shipped times 1,000,000. Made it more like calculating % defective.

Definitions

I'm trying to find out if there is a document, standard, manual or something that actually defines PPM vs. dPPM. It appears as though some people use them interchangeably and others do not. To me they are two different metrics and I was hoping that there was some sort of document out there to clarify. Anyone?

PPM and DPMO- Difference is # of opportunities

PPM- Parts or defects per million
DPMO- Defect per million opportunites

If a part has only one opportunity of producing defect then PPM & DPMO will have same meaning but if opportunities for defects are more than one, then DPMO is a preferred metric.

Arvind

My formula for defects in PPM

Total defects divided by total possible defects X 1,000,000 = DPM
eg : 42 / 728,000 = .0000576 x 1,000,000 = 57.6 DPM

calimar75 said:

I'm trying to find out if there is a document, standard, manual or something that actually defines PPM vs. dPPM. It appears as though some people use them interchangeably and others do not. To me they are two different metrics and I was hoping that there was some sort of document out there to clarify. Anyone?

Click to expand...

The really 'historical' definition is a direct result of the difference between a defect on a part and a defective part. You may have many defects on a single part. A part is defective if it has one or more defects on it.
So technically, ppm is the number of defective parts per million* and dpm is the number of defects per million parts. you can have more than 1 million dpm if you have more than 1 defect per part...but the max ppm is 1M...

dpmo is defects (not defective parts) per million opportunities fo rthe defect to occur. how the number of opportunities is caculated can be and is often hotly debated...think number of solder defects on a board with 1000 joints vs 10,000 joints. It's usefullness is somewhat restricted to direct comparisons of defect rates between two different products or processes that vary significantly in their complexity....

* ppm is also a chemical/medical/etc industry term meaning the ratio of some 'contaminant' or other element in a batch of other chemicals...slightly different meaning in that context.