First Pass Yield & RTY
Per-step FPY, Rolled Throughput Yield, DPMO, sigma level.
RTY = FPY1 × FPY2 × … × FPYn · Hidden factory = Final yield − RTY.
Ref: Harry & Schroeder, Six Sigma · Breyfogle, Implementing Six Sigma
RTY = FPY1 × FPY2 × … × FPYn · Hidden factory = Final yield − RTY.
Ref: Harry & Schroeder, Six Sigma · Breyfogle, Implementing Six Sigma
I Process Steps
Enter units inspected and defects at each step. Defects include rework, scrap, and any unit requiring correction before moving forward.
| # | Step Name | Units In | Defects | FPY |
|---|
— Reference
First Pass Yield (FPY) measures the percentage of units that pass through a process step correctly the first time, without rework, repair, or scrap. FPY = (Units In − Defects) / Units In. Unlike final yield, FPY exposes the hidden factory — rework that adds cost but not value.
Rolled Throughput Yield & Hidden Factory
RTY is the probability a unit passes through all steps defect-free: RTY = FPY1 × FPY2 × … × FPYn. Because probabilities multiply, RTY drops quickly — a 5-step process with 97% FPY per step has RTY of 85.9%. The gap between final yield and RTY is the hidden factory cost.
How to Improve RTY
- Start with the worst step — smallest FPY has the largest RTY leverage
- Pareto analysis — find the top defect types at the worst step
- Root cause analysis — 5 Why, fishbone for systematic causes
- Poka-yoke — mistake-proof the step before it reaches inspection
- SPC control charts — detect shifts before they produce defects
Yield Benchmarks
- RTY ≥ 99% — semiconductor fabrication, pharmaceutical
- RTY ≥ 95% — world-class discrete manufacturing, automotive assembly
- RTY 85–95% — competitive general manufacturing
- RTY < 85% — significant hidden factory waste; systematic improvement needed
— Frequently Asked Questions
What is First Pass Yield (FPY)?
FPY is the percentage of units that pass through a process step without any defect, rework, or scrap. FPY = (Units In − Defects) / Units In. It measures right-first-time quality and exposes the hidden factory.
What is Rolled Throughput Yield (RTY)?
RTY is the probability of a unit passing through all process steps defect-free. Multiply all FPY values: RTY = FPY1 × FPY2 × …. RTY is always ≤ the lowest individual FPY.
What is the hidden factory?
The hidden factory is the gap between final yield (which counts reworked units as good) and RTY (which only counts right-first-time). A process shipping 99% good product might have 85% RTY — the 14% gap is rework, reinspection, and sorting that adds cost without adding value.
How do I convert RTY to sigma level?
DPMO = (1 − RTY) × 1,000,000. Then apply the inverse normal distribution with a 1.5σ shift: Sigma = Φ−1(RTY) + 1.5. This calculator computes it automatically using the Abramowitz & Stegun approximation.