What Is Rolled Throughput Yield?
Rolled Throughput Yield (RTY) calculates the probability that a unit will pass through an entire multi-step process without requiring rework at any step. It multiplies the First Pass Yield of each step together.
RTY reveals a truth that individual step yields hide: even when each step looks good, the cumulative effect of defects across many steps can be dramatic.
The Formula
RTY = FPY₁ × FPY₂ × FPY₃ × … × FPYₙExample: A 4-step process with yields of 98%, 95%, 97%, and 99%:
RTY = 0.98 × 0.95 × 0.97 × 0.99 = 89.4%Every step looks good individually, but more than 1 in 10 units requires rework somewhere.
Data Requirements
| Source | Required | What You Need |
|---|---|---|
| Machine Data / MES | Yes | First Pass Yield at each process step |
RTY is a Phase 3 metric — it requires FPY tracking at every step, which typically needs MES-level data collection.
Why It Matters
- Reveals the hidden factory — the gap between RTY and final yield represents hidden rework
- Identifies the weakest link — the step with the lowest FPY has the most improvement potential
- Guides priorities — improving the worst step gives the biggest RTY improvement
- Realistic yield prediction — accounts for cumulative defect probability across all steps
The Key Insight
If your final yield is 95% but your RTY is 80%, the 15-point gap represents rework that is being done but not accounted for. That gap is the hidden factory — consuming capacity and adding cost without producing additional output.
Best Practices
- Calculate RTY for all multi-step processes
- Compare RTY to final observed yield — if they differ significantly, hidden rework exists
- Focus improvement on the step with the lowest FPY
- Track RTY improvement after process changes to validate effectiveness
- Use RTY to justify process improvement investments with financial impact
Related Metrics
- First Pass Yield — the building block of RTY
- Defect Rate — defects at each step reduce FPY and therefore RTY
- Rework Rate — the gap between RTY and final yield is hidden rework
- Scrap Rate — units that fail and cannot be reworked