How do you calculate first pass test yield?

Divide units passing first-pass test by total units tested. With 1,110 of 1,200 assemblies passing on the first attempt, FPY is 1,110 ÷ 1,200 = 92.5%.

What is a good first pass yield for PCB assembly?

Mature SMT lines often run 95-99% FPY on stable products, with new product introductions starting lower. The example's 92.5% sits 4.5 points under a 97% target, signaling a process issue worth root-causing.

What is the difference between first pass yield and final yield?

FPY counts only units that pass on the first test; final yield counts everything that eventually passes after rework. Final yield can look excellent while FPY is poor, which is exactly when hidden rework cost is highest.

Why does first pass yield matter more than final yield?

Every first-pass failure consumes a retest slot, an operator, and often a rework cycle. FPY is the leading indicator of that hidden capacity and cost, while final yield only confirms shipped quality.

How is FPY different from rolled throughput yield (RTY)?

FPY is the first-pass rate at a single test step. RTY multiplies the FPY of every process step together, so it reflects the true probability of a unit clearing the whole line defect-free in one pass.

How many assemblies does a 4.5-point FPY gap represent?

At 1,200 units tested, 4.5 points is about 54 assemblies that failed first test and entered retest or rework — every one a candidate for the diagnostic and rework labor you are trying to eliminate.

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First Pass Test Yield Calculator

First pass test yield (FPY) is the share of assemblies that pass functional or in-circuit test on the very first attempt, with no rework or retest. Test engineers and SMT line leaders in PCB and box-build operations treat it as the cleanest signal of upstream process health, because it excludes any unit that needed a second pass to make it good. Unlike final yield, FPY exposes hidden rework that final-test numbers paper over. A strong FPY means solder, placement, and component quality are right the first time, which is exactly what keeps test cells and rework benches from becoming bottlenecks.

What this calculator does

Measure first-pass test yield for PCB assemblies or electronic products against a target yield.
a quality engineer is reviewing test yield for a board family, product, or line
It computes the fraction of tested assemblies that pass on their first test attempt, plus the gap in points to your target FPY.

Formula used

First-pass test yield = units passing first-pass test ÷ total units tested
Yield gap to target = target first-pass test yield - first-pass test yield

Inputs explained

Units passing first-pass test: Use a current, same-scope value for units passing first-pass test from the traveler, MES, ERP, test log, quote, or validated engineering estimate.
Total units tested: Use a current, same-scope value for total units tested from the traveler, MES, ERP, test log, quote, or validated engineering estimate.
Target first-pass test yield: Use a current, same-scope value for target first-pass test yield from the traveler, MES, ERP, test log, quote, or validated engineering estimate.

How to use the result

Use it per line, per product, or per shift to monitor SMT and assembly process quality and to catch hidden rework load before final yield hides it.
FPY counts a unit as failed even if it later passes after rework, so a high FPY tells you nothing about whether failures are repairable — track rework yield separately.

Current U.S. benchmarks

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The U.S. has 11,261 computer and electronic products establishments employing about 815,443 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate first pass test yield? Divide units passing first-pass test by total units tested. With 1,110 of 1,200 assemblies passing on the first attempt, FPY is 1,110 ÷ 1,200 = 92.5%.
What is a good first pass yield for PCB assembly? Mature SMT lines often run 95-99% FPY on stable products, with new product introductions starting lower. The example's 92.5% sits 4.5 points under a 97% target, signaling a process issue worth root-causing.
What is the difference between first pass yield and final yield? FPY counts only units that pass on the first test; final yield counts everything that eventually passes after rework. Final yield can look excellent while FPY is poor, which is exactly when hidden rework cost is highest.
Why does first pass yield matter more than final yield? Every first-pass failure consumes a retest slot, an operator, and often a rework cycle. FPY is the leading indicator of that hidden capacity and cost, while final yield only confirms shipped quality.
How is FPY different from rolled throughput yield (RTY)? FPY is the first-pass rate at a single test step. RTY multiplies the FPY of every process step together, so it reflects the true probability of a unit clearing the whole line defect-free in one pass.

Last reviewed 2026-05-12.