First Pass Yield Calculator: Units Right the First Time
Work out first pass yield (FPY) from units that pass the first time and total units started — the quality and efficiency metric that captures how often a process gets it right without rework, with the rework/scrap share alongside.
Adjust the inputs and select Calculate for a full breakdown.
Compare Common Scenarios
How the numbers shift across typical situations for this calculator:
| Scenario | First pass yield | Rework / scrap |
|---|---|---|
| 940 of 1,000 (94%) | 94.00% | 6.00% |
| 980 of 1,000 (98%, strong) | 98.00% | 2.00% |
| 850 of 1,000 (85%, high rework) | 85.00% | 15.00% |
| 475 of 500 (95%) | 95.00% | 5.00% |
How This Calculator Works
Enter the units that passed the first time (no rework) and the total units started. The calculator divides one by the other and multiplies by 100 to give the first pass yield, with the rework/scrap share alongside. Critically, FPY counts only units that passed without any rework — reworked units that later pass do not count.
The Formula
Part as a Percentage of a Whole
Part is the portion, Whole is the total it belongs to
Worked Example
940 units passing first time out of 1,000 started is a 94% first pass yield, with 6% requiring rework or scrap. FPY differs from a simple final yield because it excludes units that needed rework, even if they eventually passed — so it exposes hidden 'rework' that final-yield numbers mask. That 6% represents real cost: wasted material, extra labor, delay, and the risk that reworked units are lower quality. A high final yield achieved through lots of rework can hide a low first pass yield and a costly, inefficient process.
Key Insight
First pass yield is a powerful metric precisely because it penalizes rework, which final-yield numbers hide. A factory might report 99% final yield, but if half the units needed rework to get there, the first pass yield is far lower — and rework is pure waste: extra labor, material, time, and quality risk. FPY makes that hidden cost visible. Two important extensions: for a multi-step process, multiply each step's FPY to get rolled throughput yield (RTY) — and because you're multiplying fractions, RTY drops fast (five steps at 95% each yield only ~77% overall), revealing how small per-step defects compound across a line. And FPY ties directly to the 'hidden factory' concept in lean/Six Sigma: the unmeasured capacity consumed by fixing defects. To improve FPY, find and eliminate root causes of defects (rather than just inspecting and reworking), use mistake-proofing (poka-yoke), and address the steps with the lowest yield first since they drag down the whole RTY. Track FPY by process step and over time; the rework/scrap complement is the cost you're driving toward zero, and improving it raises throughput and lowers cost without adding capacity.
Frequently Asked Questions
How is first pass yield calculated?
Divide units that passed the first time (no rework) by total units started, then multiply by 100. 940 passing first time out of 1,000 is a 94% first pass yield, with 6% requiring rework or scrap.
How is FPY different from final yield?
Final yield counts all units that eventually pass, including those that needed rework. First pass yield counts only units that passed without any rework. FPY exposes hidden rework that final yield masks — a high final yield achieved through lots of rework can hide a low, costly first pass yield.
What is rolled throughput yield?
For a multi-step process, rolled throughput yield (RTY) is the product of each step's first pass yield. Because you multiply fractions, RTY falls quickly — five steps at 95% each give only about 77% overall. It reveals how small per-step defects compound across a whole line or process.
Why does rework matter so much?
Rework is pure waste: extra labor, material, and time, plus delay and the risk that reworked units are lower quality. It consumes capacity that final-yield numbers don't show — the 'hidden factory.' Reducing rework (raising FPY) lowers cost and increases throughput without adding equipment or staff.
How do I improve first pass yield?
Find and eliminate the root causes of defects rather than just inspecting and reworking, use mistake-proofing (poka-yoke) to prevent errors, and tackle the lowest-yield steps first since they drag down the whole rolled throughput yield. Track FPY by step and over time to target improvements where they matter most.
Related Calculators
Methodology & Review
First pass yield is units that pass without rework divided by units started, multiplied by 100. The complement is the share requiring rework or scrap. It measures a single process step; chaining steps gives rolled throughput yield (the product of each step's FPY).
Written by Ugo Candido · Last updated May 22, 2026.