Contents
What is first pass yield?
First pass yield (FPY) — also called first-time-right rate or throughput yield — is the percentage of units that complete a process step without any defect, rework or scrap. It answers a single, brutal question: "Of everything we started, how much came out right the first time?" An FPY of 95 % sounds excellent — until you multiply it across 8 process steps and discover that your rolled throughput yield is only 66 %. FPY is the quality metric that reveals hidden rework loops the scrap report never shows.
Calculate first pass yield directly: FPY calculator
How is FPY calculated?
FPY = Good Units (no rework, no scrap) / Total Units Entering the Process
Worked example — stamping press + deburring + inspection:
- Units entering press: 1,000
- Units that required rework (burr removal beyond spec): 60
- Units scrapped: 15
- Units passed right first time: 1,000 − 60 − 15 = 925
FPY = 925 / 1,000 = 92.5 %
Critical distinction: those 60 reworked units eventually shipped as good parts. Traditional yield (final yield) would report 985 / 1,000 = 98.5 %. The plant looks great. But FPY shows the truth: 7.5 % of production consumed extra labour, extra cycle time and extra machine capacity. That hidden cost is invisible in the scrap report — and it is the reason FPY exists.
What is rolled throughput yield (RTY) and why does it matter more than single-step FPY?
Most manufacturing processes have multiple steps. RTY multiplies the FPY of each step to show the probability that a unit passes the entire process without any rework at any point.
RTY = FPY₁ × FPY₂ × FPY₃ × … × FPYₙ
| Process step | FPY | Cumulative RTY |
|---|---|---|
| 1 — Blanking | 97 % | 97.0 % |
| 2 — Forming | 95 % | 92.2 % |
| 3 — Welding | 93 % | 85.7 % |
| 4 — E-coat | 96 % | 82.3 % |
| 5 — Assembly | 94 % | 77.3 % |
| 6 — Final inspection | 98 % | 75.8 % |
Every step looks individually acceptable (93–98 %). But only 75.8 % of all units pass all six steps right the first time. Nearly one in four units fails at least one step on the first pass; this includes scrap as well as rework. RTY alone does not separate the two.
How does FPY relate to OEE?
FPY feeds directly into the Quality factor of OEE. OEE Quality counts parts produced right the first time / total parts. Reworked parts are quality losses, even if they later pass. Final yield includes successfully reworked parts; OEE Quality and FPY exclude them.
| Metric | What it counts | Reworked units are… | Reveals rework cost? |
|---|---|---|---|
| OEE Quality | Parts right first time / total parts | Counted as quality losses | Rework is a loss; cost is not quantified |
| FPY | Parts right first time / total parts entering | Counted as failures (they needed correction) | Yes — every rework loop is visible |
| RTY | FPY₁ × FPY₂ × … × FPYₙ across all steps | Compounded across process chain | Yes — full hidden factory exposed |
A final yield of 99 % can coexist with an FPY of 85 % if 14 % of units pass only after rework. Those reworked units are quality losses in OEE, even if they eventually ship.
What FPY benchmarks should a manufacturer target?
| Industry / process | Typical FPY range | What drives the range |
|---|---|---|
| Automotive stamping / forming | 90–97 % | Tool wear, material variation, setup precision |
| Injection moulding | 92–98 % | Process parameter stability, mould condition |
| Assembly (manual + semi-auto) | 85–95 % | Operator skill, component quality, poka-yoke |
| Fully automated high-speed lines | 95–99.5 % | Machine condition, SPC discipline, sensor coverage |
| Pharma packaging / blister | 93–98 % | Foil alignment, seal integrity, print registration |
The goal is not a universal target number — it is directional improvement. If your stamping FPY is 91 % today, the next milestone is 94 %.
How does an MES automate FPY measurement?
Manual FPY tracking means: operators tally defects and rework on paper, someone enters the numbers into Excel at the end of the shift, and the quality manager sees results 24–48 hours later. By then, the root cause is cold. An MES captures FPY in real time:
- Automatic count capture: Good parts, scrap parts and rework events are logged directly from the PLC — no manual tally, no end-of-shift data entry, no transcription errors.
- Defect classification at the source: When a part is rejected, the operator (or the machine itself via alarm codes) classifies the defect type. The MES builds the Pareto automatically: which defect types drive the most FPY loss?
- Real-time alerts: When FPY falls below a defined threshold (e.g., < 90 % rolling last 100 parts), the system notifies the shift leader immediately — not at the morning meeting tomorrow.
The SYMESTIC production metrics module captures good/reject counts per machine per order automatically.
FAQ
What is the difference between FPY and final yield?
Final yield counts everything that eventually ships as good — including units that were reworked. FPY counts only units that passed right the first time. Final yield flatters the process; FPY tells the truth. A process with 98 % final yield and 85 % FPY has a 13-percentage-point rework problem that is consuming capacity, labour and material without appearing in the scrap report.
How does FPY connect to DPMO and sigma level?
FPY is a unit-level metric (did the whole unit pass?). DPMO is an opportunity-level metric (how many defect opportunities per million?). A unit can fail FPY due to a single defect out of 20 possible defect opportunities. DPMO tells you which specific opportunity is failing most often; FPY tells you the overall process result. Use FPY for line-level performance tracking. Use DPMO for DMAIC root-cause analysis when you need to drill into which defect types to attack first.
Should reworked units be counted as FPY failures even if they pass final inspection?
Yes — always. That is the entire point of FPY. A reworked unit consumed extra resources. If you count it as a pass, you are measuring final yield, not FPY, and the hidden factory stays hidden. The discipline of counting rework as an FPY failure is uncomfortable — it makes the numbers look worse. But it is the only way to see the true cost of quality and drive real improvement.
Related: OEE Explained · DPMO · Six Sigma · DMAIC · Control Limits · MES: Definition & Functions · SYMESTIC Production Metrics
How many parts are right the first time?
From parts started, scrap and rework, the calculator works out first pass yield and scrap rate. No sign-up needed.
Every defect recorded, every defect costed
Scan the part, choose OK or NOK, tap the defect location. SYMESTIC shows which defect occurs how often and what it costs.