FPY = Units Completed Right First Time / Total Units Started × 100%. A step that processes 1,000 units and produces 950 good units first time, even if the other 50 were reworked into passing, has an FPY of 95%. The reworked units count as defects for this metric, even though they eventually shipped.
For a multi-step process, the true first-pass yield is the product of the FPYs at each step. A 10-step process where every step achieves 95% FPY has a rolled throughput yield of 0.95^10 = 60%. This math is uncomfortable but essential, small defect rates at individual steps compound into large system-level losses.
Final yield can be pushed to 100% by aggressive rework. That masks the fact that the process is producing defects and consuming capacity to fix them. FPY exposes the truth: how often does the process actually work correctly? Improving FPY reduces rework, scrap, cycle time and cost simultaneously, because every defect that never happens is one that doesn't need to be fixed.
First Pass Yield is a metric that resists being gamed. It rewards processes that produce quality at the source instead of relying on inspection and rework. Measured over time, it tracks the true health of a process better than almost any other single number.
A quality philosophy that aims to prevent defects rather than detect or correct them later. It emphasizes doing the work correctly the first time, every time, and building quality into every process.
Ensuring every operator verifies quality before passing work to the next process.
Designing processes so defects cannot continue downstream.
