Measuring First-Pass Yield: A Beginner-Friendly Explainer

First-pass yield (FPY) -- also called first-time quality, rolled throughput yield, or first-time right -- is the percentage of units or transactions that flow through a process without requiring rework, correction, rejection, or scrapping. A first-pass yield of 95 percent means that 95 percent of items complete the process correctly on the first attempt; 5 percent require some form of rework or correction.

First-pass yield is one of the most informative quality metrics in Lean Six Sigma because it captures all quality losses in a process, not just the units that are ultimately scrapped. An item that is reworked and eventually passed is not a quality success -- it is a quality failure that was caught and corrected at additional cost. FPY captures this cost.

Why First-Pass Yield Matters

The relationship between first-pass yield and capacity is direct and often surprising. A process with a first-pass yield of 80 percent must process 100 units to deliver 80 acceptable units -- it is consuming 20 percent of its capacity on rework rather than on value-adding production. If that process has multiple steps, the cumulative yield loss compounds: a three-step process where each step has a 90 percent first-pass yield has a total rolled throughput yield of 72.9 percent (0.9 x 0.9 x 0.9). Nearly 30 percent of capacity is consumed by rework.

How to Calculate First-Pass Yield

• For a single process step: FPY = (units completed without defects) divided by (total units started). Count only units that pass through the process without any rework, correction, or rejection.

• For a multi-step process (rolled throughput yield): multiply the FPY of each step together. If step A has a 95 percent FPY and step B has a 90 percent FPY, the rolled throughput yield of the two-step process is 85.5 percent.

• Be careful about what counts as rework. Re-inspection, approval cycles, returned work, and corrections that are completed within the same work session can all be hidden forms of rework. First-pass yield calculations that exclude these will overstate true quality.

How to Use First-Pass Yield

• Use FPY to identify which process steps have the most quality loss. The step with the lowest first-pass yield is the step where improvement effort will have the most impact on overall quality and capacity.

• Track FPY over time to measure improvement. A first-pass yield that is improving -- even slowly -- indicates that quality improvement efforts are working. A first-pass yield that is static or declining identifies a process that is not improving.

• Use FPY to quantify the cost of poor quality. The cost of rework, correction, and rejection is a direct function of the gap between current FPY and 100 percent. If rework costs an average of $50 per unit and your FPY is 90 percent, your cost of poor quality is $50 x 10 percent of total units produced.

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