Final Yield (FY) represents the acceptable pieces at the end of the process divided by the pieces started. The FY excludes scrap (so scrap is part of the calculation).
In other words, if there are the same amount of pieces at the end as there were at the start (without any being introduced in the middle) then there is perfect 100% Final Yield.
Rework is not a part of the FY calculation. Use the process map as a guide for evaluating each individual process.
FY does not depend on the number of processes involved. It is a high level determination the percentage of good pieces that came out of the entire process compared to the quantity started or that should have been made.
NOTE: Sometimes, only raw material is available at the start so it may be necessary to convert the raw material into the amount of expected pieces that it should make, or use a unit of weight at the start and weight out at the end for the calculation.
Calculation from above example:
The unit of measure must be similar for numerator and denominator throughout.
Process 1 Yield: 46 passed / 50 entered = 92.0%
Process 2 Yield (itself): 46 passed / 46 passed = 100%
Yield AFTER Process 2: 46 passed / 50 entered: 92.0%
Process 3 Yield (itself): 37 passed / 46 entered = 80.4%
Yield AFTER Process 3 (also the same as the final yield of entire process):
37 passed / 50 entered
Final Yield = 74%
Process 3 has the lowest yield and probably the most cost associated since all the material, labor, and overhead costs are already in the pieces from the previous processes.
Final Yield and other yield metrics can serve as baseline scores (Measure Phase) and final scores for Six Sigma projects (Control Phase). The baseline score does not have to be a z-score and often this yield metrics are easier for team and other company employees to relate with and understand.
CAUTION If there is known rework and it is significant to your team and company's success, then throughput yield and rolled throughput yield are better metrics.
Other Process Yield Metrics
TPY - Throughput Yield
RTY - Rolled Throughput Yield
NY - Normalized Yield
Six Sigma Modules
The following presentations are available to download.
Green Belt Program (1,000+ Slides)
Cause & Effect Matrix
Central Limit Theorem
1-Way Anova Test
Correlation and Regression