Rolled Throughput Yield (RTY) Explained

Definition: Rolled Throughput Yield (RTY) is a critical Lean Manufacturing metric that calculates the probability of a unit passing through a multi-step process without any rework or scrap. It is determined by multiplying the First Pass Yield (FPY) of every individual process step.

The Calculation (Simplified)

Instead of complex formulas, RTY uses a simple multiplication of the "good part" rates for each stage:

RTY = FPY Step 1 x FPY Step 2 x FPY Step 3 ...

Why Traditional Yield Metrics Are Often Deceptive

Most companies make the mistake of only measuring "Final Yield." If 100 blanks enter the line and 95 finished products come out, they report a 95% yield. RTY uncovers what happens in between. It asks the critical question: How many of those 95 products had to be reworked, corrected, or re-tested along the way?

While traditional yield only counts "scrap at the end," RTY exposes the Hidden Factory—the internal capacity wasted on correction loops that never show up on a standard balance sheet.

Practical Example: The Compounding Effect

Imagine a process with 5 steps. Each step looks solid with a 95% First Pass Yield (FPY). However, the mathematics of RTY is relentless:

• Step 1 (95%) * Step 2 (95%) * Step 3 (95%) * Step 4 (95%) * Step 5 (95%) = 77.4% Total Result

The Reality: Nearly one out of every four parts causes additional costs through rework or scrap, even though every individual department head is reporting a "healthy" 95%.

RTY as a Compass for Six Sigma and Lean

In process optimization, RTY serves as a high-precision diagnostic tool:

• Identifying Bottlenecks: It immediately highlights which step is dragging down the entire chain’s performance.
• Cost Transparency: It correlates directly with the Cost of Poor Quality (CoPQ).
• Process Stability: A dropping RTY is often an early warning sign of tool wear or declining process discipline, long before final scrap rates increase.

Expert Insight: RTY vs. FPY

Do not confuse RTY with a simple First Pass Yield (FPY). While FPY is an isolated snapshot of a single operation, RTY provides a systemic view. If you want to shorten your Lead Times, you must increase your RTY—because every rework loop is an unpredictable time-sink that disrupts your material Flow.

Strategic Business Value

An optimized RTY leads to:

1. Drastically Shorter Lead Times: Fewer "loops" in the process.
2. Higher OEE: Capacity is used for actual output rather than repairs.
3. Reduced Manufacturing Costs: Eliminating the hidden costs of the "Hidden Factory."