First pass yield (FPY)
The share of pieces a process gets right the first time, counted rather than assumed. Rework that was recovered still failed first pass.
Formula
In practice
Quality is stored as counts, never percentages: first-pass good, rework and scrap, which together are the total. First pass yield is the first of those over the total, so a unit that needed rework does not count towards it however good it ended up.
That is deliberately not the same figure as the quality factor inside OEE, which uses the final good count and therefore credits units recovered by rework. Where the count point sits decides which is which, and the product reports both and never substitutes one for the other — a process at 80% first pass yield and 99% final yield is a process with a rework loop somebody is paying for, and a single number would hide exactly that.
How this is calculated
Common questions
Does a unit that was reworked and passed count as good?
Not in first pass yield, and yes in the OEE quality factor. The two answer different questions: one asks whether the process got it right without intervention, the other asks how many saleable units came out of the time the equipment was given.
Why record counts instead of entering a percentage?
Because a percentage cannot be recombined. Counts let the engine derive first pass yield, final yield and scrap rate from one entry, propagate demand backwards through yield loss, and tell rework apart from scrap — none of which survives being handed a single ratio.
Related terms
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Rolled throughput yield
The chance a piece passes every process first time, all of them multiplied together. Falls faster than any single yield…
This definition is the one the product itself shows, read from its interface catalogue at build time.