What is First Pass Yield (FPY)? Definition & Manufacturing Examples

What is First Pass Yield?

First pass yield (FPY) is the percentage of units that complete a manufacturing process correctly the first time without requiring rework, repair, retesting, or being scrapped. It measures how well a process produces good output on the initial attempt. An FPY of 95 percent means that 95 out of every 100 units entering the process exit as conforming product without any additional processing. FPY is one of the most direct measures of process quality and manufacturing efficiency.

How First Pass Yield Works

FPY is calculated at a single process step:

FPY = Good Units (first attempt) / Total Units Entering the Process

For a multi-step process, the overall quality metric is called rolled throughput yield (RTY), calculated by multiplying the FPY of each individual step. If a three-step process has FPY values of 98 percent, 95 percent, and 97 percent, the RTY is 0.98 x 0.95 x 0.97 = 0.903, or 90.3 percent. This means only 90.3 percent of units pass through all three steps without any rework — even though each individual step looks good in isolation.

RTY reveals the hidden factory — the rework loops, extra inspections, and repair operations that consume capacity without adding value. A process with six steps at 95 percent FPY each has an RTY of only 73.5 percent, meaning more than one in four units requires rework or special handling somewhere in the process.

FPY is tracked per operation, per machine, per operator, and per product. Trends over time reveal whether process improvements are working. Sudden drops flag equipment issues, material problems, or training gaps. Comparing FPY across machines running the same product identifies equipment that needs calibration or maintenance.

First Pass Yield Example

A printed circuit board (PCB) assembly line has four main process steps: solder paste application, component placement, reflow soldering, and automated optical inspection (AOI). The team tracks FPY at each step over a production run of 2,000 boards:

Solder paste: 1,980 pass / 2,000 entered = 99.0% FPY. Component placement: 1,940 pass / 1,980 entered = 98.0% FPY. Reflow soldering: 1,891 pass / 1,940 entered = 97.5% FPY. AOI: 1,834 pass / 1,891 entered = 97.0% FPY.

RTY = 0.99 x 0.98 x 0.975 x 0.97 = 91.7 percent. Out of 2,000 boards that started, only 1,834 passed all four steps on the first attempt. The remaining 166 boards required rework — technicians spending time diagnosing and repairing defects, then sending boards back through inspection.

At an average rework cost of $12 per board (labor plus retest), the rework adds $1,992 to the production run. If the team improves component placement FPY from 98.0 to 99.5 percent by upgrading nozzles and improving feeder maintenance, RTY rises to 95.0 percent, reducing rework boards from 166 to 100 and saving approximately $792 per run.

Why First Pass Yield Matters for Production Scheduling

Low FPY creates scheduling chaos. Every unit that fails inspection and enters a rework loop consumes additional machine time, labor, and queue space that was not in the original schedule. Rework jobs compete with new production for the same resources, pushing other jobs back and threatening due dates.

Scheduling software like Resource Manager DB (RMDB) can account for expected scrap and rework by inflating production quantities — if FPY is 95 percent and the customer needs 1,000 units, the system schedules 1,053 units to ensure enough good parts emerge. However, this is a compensating control, not a solution. The real solution is improving FPY to reduce the need for overproduction.

High FPY makes schedules more predictable. When nearly every unit passes on the first attempt, the actual production timeline matches the planned timeline, due dates are reliable, and capacity is not consumed by unplanned rework.

Related Terms

• Scrap Rate — The percentage of production that cannot be reworked and must be discarded
• Rework — The process of correcting defective units, a direct consequence of low FPY
• Overall Equipment Effectiveness — A composite metric that includes quality rate, which is closely related to FPY

Frequently Asked Questions

Learn more in our complete manufacturing glossary or production scheduling guide.