What Does First Pass Yield Mean in Six Sigma?

First pass yield, or FPY, is the fraction of units that complete a process step correctly the first time — no rework, no repair, no scrap, no quiet second attempt. If 1,000 units enter and 850 emerge right without being touched twice, first pass yield is 85 percent, regardless of how many were eventually fixed and shipped. It is the honest sibling of traditional yield, which counts salvaged units as successes.

How it works

The calculation is units right the first time divided by units entering the step. The definition’s teeth are in what counts as a failure: a unit that is reworked and then passes still counts against first pass yield, because the process needed two attempts. This is what separates FPY from final yield, which asks only whether a unit shipped. Final yield measures outcomes; first pass yield measures the process.

FPY is computed per step, which is what makes it diagnostic. A single overall figure says the process struggles; a per-step profile says where. It also feeds directly into rolled throughput yield — the product of first pass yields across all steps — which turns local measurements into a system-level verdict. Service teams sometimes call the same idea right first time, tracked as the share of cases closed without a bounce-back.

A worked example

An illustrative office case: an accounts team processes 1,000 invoices in a month. Of these, 120 bounce back to requesters for missing purchase-order numbers and are later resubmitted and approved, while 30 are abandoned entirely. Traditional final yield looks excellent: 970 of 1,000 invoices ultimately processed, or 97 percent. First pass yield tells the truth: only 850 of 1,000 cleared without a second touch — 85 percent. The twelve-point gap is the hidden factory — the emails, the waiting, the resubmissions, and the clerk-hours that vanish into “handled.” The improvement target is now visible, and it has a number.

• Counting reworked units as passes — the most common way FPY gets flattered
• Measuring only at final inspection instead of at each step
• Defining “right the first time” loosely, so different people count differently
• Ignoring service processes — invoices, applications, and tickets have yields too
• Improving FPY by inspecting harder rather than erring less — the defect rate has not moved, only its discovery point

Final yield tells you what shipped; first pass yield tells you what shipping cost.

First pass yield enters the toolkit at Yellow Belt ($129, about 14 hours) and becomes a working instrument at Green Belt, where the Measure phase of the simulated project has you computing FPY step by step and rolling it up. It is among the fastest metrics to learn and among the hardest to unsee — our free White Belt defines it in the core vocabulary module.