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Manufacturing & operations

Scrap rate calculator — scrap %, first pass yield and RTY

Calculate scrap rate, first pass yield and rolled throughput yield across every step. See the annual cost of scrap and how many units to start.

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Short answer

Scrap rate is scrap units ÷ units started × 100. First pass yield is the units that clear every step with no rework, and rolled throughput yield is the step yields multiplied together. 640 scrap out of 24,000 started is a 2.7% scrap rate; four steps at 99.1%, 98.4%, 97.6% and 99.3% roll up to 94.5%.

Scrap gets reported as a percentage because a percentage sounds small. This scrap rate calculator converts it into the three numbers that change decisions: what first pass yield really is once rework is counted, what the whole routing delivers end to end, and what the loss costs you a year.

Enter units started, scrap and rework, the cost you carry per scrapped unit, and the yield of each step in the routing. You get scrap rate, first pass yield, rolled throughput yield, the annualised cost of scrap, and the release quantity needed to land a target number of good units.

Your numbers

units

Units released into the process, not units completed. Completions already exclude the scrap.

units

Destroyed or downgraded beyond use. Record them at the operation where the loss happened.

units

Failed, went back, eventually passed. Not scrap — but not first-time-good either.

$

Material plus conversion absorbed up to that operation.

$

Regrind, remelt or B-stock recovery.

periods

12 if the figures above are monthly, 52 if weekly.

Rolled throughput yield

Operations a unit must clear. Yields multiply, they never average.

%
%
%
%
units

What the customer needs to receive. The tool works back to the release quantity.

Plan the release using

Result

Scrap rate
2.7%

640 scrap units from 24,000 started, at $16.30 of net cost each

First pass yield (no rework)95.8%
Yield after rework97.3%
Rolled throughput yield (4 steps)94.5%
Cost of scrap this period$10,432
Annualised cost of scrap$125,184
Units to start for 20,000 good21,163 (+1,163)
Step 1 loss0.90%
Step 2 loss1.60%
Step 3 loss2.40%
Step 4 loss0.70%
Releasing 21,163 units to finish 20,000 good ones.
Routing stepYieldCumulative RTYUnits out
Step 199.1%99.1%20,973
Step 298.4%97.5%20,637
Step 397.6%95.2%20,142
Step 499.3%94.5%20,001
Scrap rate = 640 ÷ 24,000 = 2.7%
First pass yield = (24,000 − 640 − 380) ÷ 24,000 = 95.8%
RTY = 99.1% × 98.4% × 97.6% × 99.3% = 94.5%
Scrap cost = 640 × ($18.40 − $2.10) = $10,432 per period = 2.4% of production cost
Annualised = $10,432 × 12 periods = $125,184
Units to start = 20,000 ÷ 94.5% = 21,163
2.7% scrap plus 1.6% rework is ordinary, and it is worth $125,184 a year. Step 3 at 97.6% is the weakest link in the routing. Also note you must release 21,163 units to ship 20,000.

Everything is computed in your browser. Nothing you type is sent anywhere or stored.

The formula

Scrap rate = Scrap units ÷ Units started × 100 · First pass yield = (Started − Scrap − Rework) ÷ Started · Rolled throughput yield = Yield₁ × Yield₂ × … × Yieldₙ · Units to start = Target good units ÷ Yield
Units started
Units released into the process, not units completed. Using completions as the denominator understates scrap.
Scrap units
Units destroyed or downgraded. Count them where the loss happened, because cost per unit differs by step.
Rework units
Units that eventually passed but needed a second pass. Not scrap, and not first-time-good either.
Step yield
Units leaving a step ÷ units entering it, for one step only.
Net cost per scrap unit
Material plus conversion cost incurred up to the scrap point, minus any salvage or recovery value.

First pass yield and rolled throughput yield answer different questions. FPY is one process, first time, no rework. RTY is the whole routing: multiply the step yields, never average them. Four steps at 97.6% each look fine individually and deliver 90.7% end to end.

Worked example

Units started
24,000
Scrap units
640
Rework units
380
Cost per unit at scrap point
$18.40
Salvage value per scrap unit
$2.10
Step yields
99.1%, 98.4%, 97.6%, 99.3%
Target good units
20,000
Result
Scrap rate 2.7% · FPY 95.8% · RTY 94.5% · $125,184 a year · start 21,167

640 ÷ 24,000 = 2.7% scrap rate. Strip out the 380 reworked units too and first pass yield is 22,980 ÷ 24,000 = 95.8% — the honest measure, since rework consumed labour nobody billed for. Across the routing, 99.1% × 98.4% × 97.6% × 99.3% = 94.5% RTY, and step three at 97.6% is the worst offender. Each scrap unit costs $18.40 − $2.10 = $16.30, so 640 units is $10,432 a month, $125,184 a year. To ship 20,000 good units you must release 20,000 ÷ 94.5% = 21,167 — 1,167 extra units of material, capacity and labour.

How this scrap rate calculator handles rework

Rework is where yield reporting usually goes wrong. A unit that failed, went back and passed on the second attempt is a good unit in the finished-goods count and a hidden cost everywhere else: extra labour, extra machine time, extra inspection, and a delivery date that moved. First pass yield excludes it. Final yield does not.

MeasureFormulaExampleWhat it tells you
Scrap rateScrap ÷ started640 ÷ 24,000 = 2.7%Material and cost destroyed
First pass yield(Started − scrap − rework) ÷ started22,980 ÷ 24,000 = 95.8%How often the process works the first time
Final yield(Started − scrap) ÷ started23,360 ÷ 24,000 = 97.3%What reaches finished goods, rework included
Rolled throughput yieldYield₁ × … × Yieldₙ99.1% × 98.4% × 97.6% × 99.3% = 94.5%Odds a unit clears the whole routing untouched
Four measures of the same run. The gap between FPY and final yield is your hidden rework factory.

Why rolled throughput yield is always worse than you expect

Step yields multiply, they do not average. Ten steps at 99% each give 90.4% RTY, which means one unit in ten touches a rework loop or a scrap bin somewhere. This is the arithmetic behind "every step looks fine but we never hit the schedule": no individual operation is failing, and the routing still leaks.

StepsEach step at 99%Each step at 97%Each step at 95%
3 steps97.0%91.3%85.7%
5 steps95.1%85.9%77.4%
10 steps90.4%73.7%59.9%
20 steps81.8%54.4%35.8%
Rolled throughput yield by step count. Long routings punish small per-step losses hard.

Costing scrap properly

  • Material at the scrap point, not the finished standard cost. A casting scrapped before machining costs the casting.
  • Conversion cost already absorbed — labour and machine hours consumed up to that operation. This is the part most scrap reports omit.
  • Less salvage or recovery — regrind, remelt, downgrade to B-stock. Net it off, and hold the recovery rate honest.
  • Plus the replacement capacity the rework consumed on the constraint, if you are capacity-limited. That hour is worth its contribution, which is what the downtime cost calculator prices.
  • Plus scrap allowances in the BOM, which quietly inflate standard cost on every part. See the BOM cost rollup calculator.

Units to start, and the trap inside it

To finish a target quantity you release target ÷ yield, not target × (1 + scrap %). At 94.5% yield, 20,000 good units need 21,167 starts — grossing up by 5.5% instead of dividing releases only 21,100 and leaves you 63 good units short. Which yield you divide by matters: use rolled throughput yield when the units travel a full routing, and the observed period yield when you are planning a single stage you have real history for.

Treat the yield loss as capacity loss as well: those 1,167 extra units occupy the same machines as the good ones, which shortens your effective takt time and eats headroom you thought you had. Getting to that level of detail is the hard part, because scrap quantity by operation, rework hours, salvage credits and the cost absorbed to that point sit in four different places in most ERPs — which is why scrap reporting so often stops at one plant-level percentage. answers the operation-level version, "first pass yield and scrap cost by operation for the last six months, worst ten items", from your own data, read-only, with the SuiteQL shown so quality and finance can settle the definition before they argue about the number.

Frequently asked questions

How do you calculate scrap rate?

Divide scrap units by units started and multiply by 100. With 640 scrap units from 24,000 started, the scrap rate is 2.7%. Use units started as the denominator, not units completed — completions already exclude the scrap, which makes the rate look lower than it is. Some plants also report scrap by value rather than count.

What is the difference between first pass yield and rolled throughput yield?

First pass yield covers one process: units that pass first time, with no rework, divided by units started. Rolled throughput yield covers the whole routing and is the product of every step yield. Four steps at 99.1%, 98.4%, 97.6% and 99.3% give an RTY of 94.5%, well below any individual step.

How many units should I start to get a target number of good units?

Divide the target by your yield: 20,000 good units at 94.5% yield needs 20,000 ÷ 0.945 = 21,167 starts. Do not add the scrap percentage instead — grossing 20,000 up by 5.5% gives 21,100 and leaves you short. Use rolled throughput yield when the units pass through a multi-step routing.

Should rework count as scrap?

No, but it must not count as first-time-good either. Rework units eventually pass, so they are not scrap, yet they consume extra labour, machine time and lead time. Keep them in a separate bucket: scrap rate measures destroyed units, first pass yield measures how often you got it right without a second attempt.

What is a good scrap rate?

It depends entirely on process and stage. Precision machining and electronics assembly often run well under 1%, while casting, forging and early-stage food processing routinely accept several percent as inherent. The useful comparison is your own trend by item and operation, plus the cost per scrap unit — 0.5% at a late operation can cost more than 3% at the first.

How do you calculate the cost of scrap?

Multiply scrap units by the cost already absorbed at the point of loss — material plus labour and overhead up to that operation — then subtract salvage value. At $18.40 absorbed and $2.10 recovered, 640 units cost $10,432 a month, or $125,184 a year. If the constraint is capacity-limited, add the lost contribution from the capacity the scrap consumed.

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