Scrap Rate Calculator
Scrap, rework, first pass yield and the cost of what you throw away.
First pass yield
89.0%
- Scrap rate
- 4.20%
- Rework rate
- 6.80%
- Final yield
- 95.80%
- Units good after scrap
- 958 units
- Scrap cost
- $504
Scrap rate and first pass yield answer different questions, and confusing them is how plants end up reporting a 98% yield while losing money. Scrap rate counts what you threw away. First pass yield counts what came out right the first time, without rework — and rework is where most of the hidden cost lives, because it consumes capacity that never appears in the output number.
This calculator reports all four figures together, plus the scrap cost at your stated unit cost. The gap between first pass yield and final yield is the rework burden: units that eventually ship but only after passing through the process a second time. If that gap is wide, your quality problem is not scrap, it is invisible factory-inside-the-factory capacity consumption.
How the result is calculated
FPY = (Units started − Scrapped − Reworked) ÷ Units started- Scrap rate = Scrapped ÷ Units started
- Rework rate = Reworked ÷ Units started
- First pass yield = (Started − Scrapped − Reworked) ÷ Started
- Final yield = (Started − Scrapped) ÷ Started
- Scrap cost = Scrapped × Cost per unit
Variables
| Symbol | Meaning | Unit |
|---|---|---|
FPY | First pass yield | % |
N | Units started | units |
S | Units scrapped | units |
R | Units reworked | units |
Worked example
A moulding cell starts 1,000 units in a shift. 42 are scrapped and 68 need rework before they can ship. Each scrapped unit has consumed $12 of material and processing.
- Scrap rate = 42 ÷ 1,000 = 4.2%
- Rework rate = 68 ÷ 1,000 = 6.8%
- First pass yield = (1,000 − 42 − 68) ÷ 1,000 = 890 ÷ 1,000 = 89.0%
- Final yield = (1,000 − 42) ÷ 1,000 = 95.8%
- Scrap cost = 42 × $12 = $504 per shift
First pass yield is 89.0% while final yield is 95.8%. The 6.8-point gap is rework, which consumes capacity without appearing in the scrap number — and at three shifts a day the $504 scrap cost becomes roughly $33,000 a month.
What this calculation does not cover
- Single-stage yield. For a multi-step process, rolled throughput yield (RTY) is the product of each step’s first pass yield, and it is always lower than the worst individual step — five steps at 95% each gives 77% overall.
- Scrap cost at material cost only understates the real loss, because it ignores the capacity that was consumed producing the scrapped unit. Adding machine hour rate gives a truer figure.
- Rework is treated as recoverable here. If rework consumes significant capacity or carries a higher defect risk, model it as scrap plus a separate rework cost line.
- Units started is the denominator. Using units completed shifts the ratio and makes performance look better when work in process is growing.
Frequently asked questions
What is the difference between scrap rate and first pass yield?
Scrap rate counts units that are thrown away, expressed against units started. First pass yield counts units that came out right first time — it treats rework as a failure too, because the unit consumed capacity twice. A plant can have a 2% scrap rate and an 82% first pass yield, and the second number is the one that explains its capacity problems.
How do I calculate rolled throughput yield?
Multiply the first pass yield of every step in the process. If five steps each run at 95% first pass yield, RTY = 0.95⁵ ≈ 77.4%. This is why improvement programmes that fix one step in isolation often show no change in final output — the loss is distributed across the whole chain.
Should rework count as good production?
For revenue purposes, yes, eventually. For capacity and quality analysis, no. Rework is work that should not have been necessary, and treating it as normal production hides both the capacity it consumes and the root cause generating it. Report it separately and track the trend.