PlantOps BI

KPI Library / Quality

First Pass Yield (FPY)

Formula: Units passing a process step correctly on the first attempt ÷ total units started
Typical range: 90%+ is solid for most discrete assembly steps; below 80% signals a process or training gap worth a root-cause pass

First pass yield (FPY) measures the percentage of units that clear a process step correctly the first time, with no rework, no repair loop, and no scrap. It is measured at a single station or test, which makes it a sharper diagnostic than an end-of-line pass rate that only tells you something failed somewhere upstream.

What good looks like

Individual stations running 90% or higher FPY are typical in a healthy discrete assembly process. Below 80%, the pattern is usually a process or training gap rather than random variation, and it’s worth a formal root-cause pass rather than another round of operator reminders.

The number that gets misread most often is rolled throughput yield (RTY): the product of every station’s FPY along the line. A plant with five stations each running a respectable 95% FPY has an RTY of roughly 77%, because the failures compound. Reporting each station’s FPY without also showing RTY lets a plant look healthy station by station while shipping a surprisingly high rate of units that failed somewhere along the way.

First Pass Yield in Power BI (DAX)

With a station-level inspection fact carrying a pass/fail flag per unit per station:

Units Started = DISTINCTCOUNT ( fact_station_inspection[unit_id] )

First Pass Units =
CALCULATE (
    DISTINCTCOUNT ( fact_station_inspection[unit_id] ),
    fact_station_inspection[pass_first_attempt] = TRUE ()
)

FPY % = DIVIDE ( [First Pass Units], [Units Started] )

RTY % =
PRODUCTX (
    VALUES ( dim_station[station_id] ),
    CALCULATE ( [FPY %] )
)

PRODUCTX over the station dimension is what turns individual station FPYs into a true end-to-end yield; a simple average across stations will overstate RTY every time.

Common mistakes

  1. Counting a minor in-line adjustment as a first pass. If an operator tweaks a fitting without logging it as rework, the unit shows up as first-pass when it wasn’t.
  2. Reporting station-level FPY as if it were end-to-end yield. That number is RTY, not FPY, and the two can differ by 20 points or more on a line with several stations.
  3. Dropping scrapped units from the denominator. Excluding units that failed and were never recovered flatters FPY by only counting the survivors.