What FPY and RTY are
First pass yield (FPY) is the percentage of parts approved the first time at a process step, without rework or scrap. Rolled throughput yield (RTY) is the combined yield of all steps in series: the probability that a part goes through the whole flow without rework.
First pass yield and RTY visual map
The map shows the formulas, the calculation and the parts funnel.
Formulas
FPY = good parts the first time ÷ parts entered
RTY = FPY1 × FPY2 × FPY3 × ...
Example: three steps
| Step | FPY | Parts continuing without rework |
|---|---|---|
| Input | 1,000 | |
| Step 1 | 95% | 950 |
| Step 2 | 98% | 931 |
| Step 3 | 90% | 838 |
RTY = 0.95 × 0.98 × 0.90 ≈ 83.8%. Out of every 1,000 parts, only about 838 get through the process without any rework.
The hidden factory
If rework recovers the parts, final yield can approach 100% and the problem vanishes from reports. But rework consumes time, labor, capacity and material: it is a "hidden factory" running inside the plant. RTY exposes that cost, which belongs to the cost of quality.
How to improve
- Attack the step with the lowest FPY first (step 3, at 90%, in the example).
- Use a Pareto chart on that step's defects.
- Apply poka-yoke and standardized work.
- Record all rework, even small fixes.
Common mistakes
- Looking only at final yield.
- Ignoring rework.
- Not measuring by step.
- Confusing output volume with quality.
Frequently asked questions
What is first pass yield?
The percentage of parts approved the first time at a step, without rework.
What is rolled throughput yield?
The product of the FPY of all steps: the combined yield of the process.
What is the RTY in the example?
0.95 × 0.98 × 0.90 ≈ 83.8%.
What is the hidden factory?
Rework that consumes resources but does not show up in final yield.
Why is RTY lower than each FPY?
Because the losses of each step multiply along the flow.
Sources
- GEORGE, M. L. et al. The Lean Six Sigma Pocket Toolbook. New York: McGraw-Hill.
- PYZDEK, T.; KELLER, P. The Six Sigma Handbook. New York: McGraw-Hill.
- BREYFOGLE, F. W. Implementing Six Sigma. Hoboken: Wiley.
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About the author
Lean Manufacturing & Behavioral Management Specialist
Over 20 years in the automotive and metalworking industries (GM and Dana), Lean Manufacturing practitioner since 2006. SENAI instructor and mentor in Brazil’s Brasil Mais Produtivo program, delivering consulting, training and audits for 50+ companies, combining quality, productivity and people development.