Quality
What is First pass yield?
First pass yield is the share of units that pass a step right first time. Learn FPY and rolled throughput yield formulas and use the free FPY and RTY calculator.
Quick answer
First pass yield (FPY) is the percentage of units that complete a process step right first time, with no rework, repair or scrap. It equals units good first time divided by units entering the step. Rolled throughput yield (RTY) multiplies the first pass yields of every step in the process.
Updated 30 October 2026. Written by the Ajinkya Technologies engineering team, reviewed by Amey Kadle.
Formula
FPY = units good first time ÷ units entering the step. RTY = FPY₁ × FPY₂ × … × FPYₙ
Worked example: 1,000 parts enter a machining step and 940 pass inspection without rework: FPY = 94%. If the next two steps have FPY of 97% and 99%, RTY = 0.94 × 0.97 × 0.99 = 90.3%, so only about 9 in 10 parts get through the whole process untouched.
First pass yield and RTY calculator
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- First pass yield
- 94.0%
- Not right first time
- 60,000 PPM
- Rolled throughput yield
- 90.3% across 3 steps
First pass yield explained
Final yield, the share of units that eventually ship, hides the cost of fixing things along the way. A part that was reworked twice still counts as good in final yield. First pass yield counts it as a failure, which is why it exposes what quality engineers call the hidden factory: the people, machines and time spent repairing work that should have been right the first time.
Rolled throughput yield extends the idea to the whole process. Because the probability of passing every step is the product of the step yields, a process with ten steps at 98% each has an RTY of only about 82%. Small losses at each step compound, so improvement effort is best directed at the steps with the lowest FPY and the highest cost of failure.
FPY needs reliable data about what happened to each unit at each step: passed, reworked, repaired or scrapped. Paper checksheets usually record defects but not rework loops, so FPY looks better on paper than on the floor. Inline inspection and part level traceability give the true figure, and defect Pareto charts show which failure modes to attack first.
Key concepts
- Right first time, no rework or repair
- RTY is the product of step yields
- Exposes the hidden factory
- Needs unit level pass, rework and scrap data
- Feeds the OEE quality factor
Questions
What is the difference between first pass yield and final yield?
Final yield counts every unit that eventually ships, including reworked ones. First pass yield counts only units that passed without any rework or repair, so it is always equal to or lower than final yield.
What is a good first pass yield?
It depends on the process and product. The useful target is steady improvement on your own baseline with a consistent definition of what counts as rework.
How is FPY different from the OEE quality factor?
The OEE quality factor is good units divided by total units at a machine, usually counting scrap and rework as not good. FPY applies the same idea to any process step, including manual ones.
How do you calculate defects per million from FPY?
Units not right first time per million equals (1 minus FPY) multiplied by 1,000,000. An FPY of 94% means 60,000 units per million needed rework or were scrapped.
References
How we help with FPY
Our quality and traceability systems record pass, rework and scrap for every unit at every step, so first pass yield and RTY are calculated automatically and linked to the defect, the machine and the batch.
Set the reject threshold yourself and watch escapes trade against false rejects (simulated data).
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