First Pass Yield (FPY)

Last updated: Oct 25, 2025

What is First Pass Yield?

First Pass Yield (FPY) measures the percentage of units that meet specifications and pass inspection on their first attempt with no rework or repair. It shows how consistently your process produces conforming output and how much hidden capacity is lost to scrap, fixes, and retests. Track FPY at a step, line, or plant level, and segment it by product, shift, supplier, or machine to find where right?first?time quality breaks down.

First Pass Yield Formula

ƒ Count(Units that pass the step on the first attempt) / Count(Units that enter the step)

ƒ Count(Units that pass final inspection on the first attempt) / Count(Units that enter the line)

How to calculate First Pass Yield

You start a work order of 1,000 units. At the functional test station: * 920 units pass on the first attempt * 60 units fail, get repaired, then pass on a second attempt * 20 units are scrapped Step FPY at functional test = 920 ÷ 1,000 = 92.0% Overall yield at that station (counting repaired units as good) would be (920 + 60) ÷ 1,000 = 98.0%. The gap between 98.0% and 92.0% shows the real workload hidden in rework and retest. Notes: You can either calculate FPY as a single step or as the full line (all steps).

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What is a good First Pass Yield benchmark?

Use internal histories rather than generic industry targets. Compare families with similar complexity, automation, and test coverage. As a rule of thumb, treat the best performing family in your plant as the near?term standard for similar products, then push the rest toward that level with focused problem?solving. Revisit targets after major design or supplier changes.

More about First Pass Yield

FPY is a quality and efficiency signal rolled into one. When FPY rises, more of your throughput ships without extra handling, so cycle time falls and costs shrink. When FPY drops, teams spend time diagnosing defects, reworking units, and queueing for retest. The same line looks busy, yet fewer good units ship.

Define the scope and terms

Set definitions so measurement is consistent:

First pass: The first time a unit completes a step or process and is checked against its acceptance criteria.
Pass: The unit meets spec and needs no rework or repair before moving on or shipping.
Rework or repair: Any additional activity on a nonconforming unit to bring it back into spec, including adjustments, component swaps, re-soldering, polishing, or software reflashing.
Scrap: Units that cannot be economically recovered.

Make these definitions visible on traveler sheets, routing instructions, and test plans. That brings alignment when teams discuss results across shifts and cells.

Where FPY sits among related metrics

FPY gets mixed up with other yields. Use clean distinctions:

Step FPY: Right?first?time rate for a single operation or test station.
Line or process FPY: Right?first?time rate across a full routing from first operation to final inspection.
Rolled Throughput Yield (RTY): The probability a unit passes every step first time, found by multiplying the step?level yields. RTY is stricter and often lower than line FPY because it models the compound chance of success.
Overall Yield: Often counts reworked units as good once they eventually pass. That can mask quality issues by inflating the result.

When you present FPY, state if reworked units are excluded from the numerator and how the denominator is defined. That avoids debates about “which yield” you reported.

How to measure FPY by manufacturing style

Discrete assembly: Count units entering the step or line, then count how many leave conforming on the first attempt. Log rework tickets and retest counts separately. Use serial numbers to prevent double counting.
Process or continuous manufacturing: Measure by batch or lot. A batch fails first pass if any material must be reprocessed, blended back, or adjusted to meet spec. For inline tests, use sample plans that represent the full run and note test coverage so you don’t overstate FPY.
High?mix, low?volume: Segment FPY by family, complexity tier, or option content. Comparing a simple subassembly to a complex box build will mislead your decisions.

Data you need

Units started and units exiting each step or the full line
First?pass accept counts at each inspection or test
Rework codes, repair durations, and retest counts
Scrap counts and reasons
Context tags: product, revision, work order, shift, operator, machine, fixture, supplier lot

Good identifiers connect these data sets. Serial numbers or robust lot tracking make FPY trustworthy and auditable.

How to use FPY in operations

Focus improvement: Rank process steps by FPY impact using a simple Pareto: where do most first?pass failures originate by defect code or station.
Protect takt time: Stations with low FPY consume buffer time with fixes and retests. Shield the pacemaker by solving upstream failure modes first.
Control incoming quality: When FPY dips after a supplier change or component revision, check incoming inspection and supplier PPAP or FAI records.
Balance with capacity: A small FPY gain can free substantial capacity if retest and rework queues vanish. That headroom often beats buying another tester.
Pair with cost of poor quality: Convert FPY misses into scrap and rework cost to show business impact. Include labour, components, consumables, and retest time.

Common pitfalls

Counting reworked units as first?pass successes: If a unit failed and then passed after repair, it does not belong in the FPY numerator.
Mixing unit defects and defective units: If you log multiple defects per unit, deduplicate to the unit level before calculating FPY.
Sampling bias: Testing only a subset of units and treating the result as full coverage will inflate FPY. Note the sample fraction and use control charts to confirm stability.
Hidden retest loops: Some stations loop a unit through the same test program multiple times. Treat any additional attempt as not first pass.
Scope creep: Report whether FPY covers the full routing or a subset. Teams make better decisions when the boundary is unambiguous.

Targets and interpretation

There is no universal target. Complexity, supplier mix, automation level, and test coverage drive the achievable range. Mature, repetitive processes tend to sustain higher FPY than high?mix, complex builds. Establish a baseline from the last 60–90 days for each family, then set staged improvements. Gains of one to two percentage points per quarter are realistic when you remove a few dominant failure modes.

Treat FPY as both a quality and flow indicator. Improving FPY reduces queues, shortens lead time, and stabilizes schedules. When you hold throughput constant, higher FPY usually lowers cost per good unit and raises delivery reliability.

First Pass Yield Frequently Asked Questions

Is FPY the same as First Time Yield (FTY) or Rolled Throughput Yield (RTY)?

Teams often use FPY and FTY interchangeably to mean right?first?time output at a step or the end of a line. Many organizations treat them as synonyms. Others reserve FTY for the end?to?end line result and use FPY for a single operation. RTY is different. RTY multiplies the first?pass yields at each operation to estimate the probability that a unit will make it through every step the first time. RTY is usually lower because it compounds small losses across many stations. To prevent confusion, publish your definitions along with the metric. State whether the number is step?level or line?level, and whether reworked units are excluded from the numerator. Once defined, lock the meaning in your dashboards and standard reports.

Should reworked units be counted in FPY once they pass?

No. FPY recognizes only those units that meet spec the first time. If a unit fails, gets repaired, and then passes, it increases overall yield but not FPY. Keeping the denominator as the original input and limiting the numerator to first?pass accepts is what makes FPY sensitive to the real cost of quality. Treating reworked units as first?pass successes hides the queues, extra handling, component waste, and retest time that erode throughput. Track rework and retest as separate measures and link them to cost of poor quality. That clarity helps you prioritise fixes that remove failure modes rather than polishing them away with more inspection.

How do you measure FPY when only a sample of units is tested?

Many processes rely on sampling plans for cost or speed. Sampling can work, but you need guardrails. First, document test coverage as a percentage of total output and display it near the FPY result so readers don’t assume 100 percent coverage. Second, use consistent sampling rules tied to risk and process capability, not convenience. Third, control for sampling bias. If only the quickest or straightest?through units get tested, FPY will look better than reality. Rotate sample selection, use time?based pulls, and cross?check with downstream defect catches. When the process or mix changes, re?validate the sampling plan before trusting the new FPY pattern.