First-Pass Yield (FPY)

First-Pass Yield (FPY) is the percentage of parts started in a production process that pass quality inspection at the first attempt without rework or repair. Formula: FPY = (input − defectives − reworked − repaired) / input. It can be defined for a single station; in multi-station systems, each station's FPY is computed separately and multiplied to obtain Rolled Throughput Yield (RTY): RTY = FPY₁ × FPY₂ × … × FPYₙ. This product rule is critical: even if every station runs at 95% FPY, a 10-station line gives RTY = 0.95¹⁰ ≈ 0.60, meaning 40% of the system is caught in rework traffic. FPY is a one-shot summary KPI for rework cost, lost throughput, customer complaints, and hidden capacity loss, and is one of the central metrics of six sigma. In an SMB context, FPY improvement is often the highest-ROI action area because every rework brings double cost (lost capacity + repair cost). Root causes that depress FPY: uncalibrated equipment, untrained operator, faulty raw material, design tolerance mismatched with process capability (low Cp/Cpk). FPY is the operational outcome of assembly line balancing, job-shop scheduling, and quality-control problems. In six sigma it ties to DPMO (defects per million opportunities): 99.9966% FPY ≈ 3.4 DPMO. References: Juran 'Juran's Quality Handbook' (1951 and later editions); Pyzdek and Keller 'The Six Sigma Handbook' (2003); Crosby 'Quality Is Free' (1979).