Rework Cost per Part: How to Calculate It, and Why It Is Not Scrap
The formula for rework cost per part, how to tell a part you can save from a part you must throw away, and why merging the two overstates cost every single time.
A part that came out wrong but can still be saved - touched up, rewelded, repainted, remachined - costs real money, but it costs money in a different shape from a part you throw away. This guide shows how to price that, and where the line between the two runs.
Rework and scrap differ on one question
The question is: does that part still get sold in the end?
| Scrap | Rework | |
|---|---|---|
| What happens to the part | Thrown away | Still sold |
| Does a replacement have to be made? | Yes | No |
| Formula | Grossed up by the defect rate - you must make extra to ship enough | Straight multiplication - only the repair effort is added |
| What is lost | Everything already spent on that part | Only the extra labor and materials used in the repair |
Rework
Parts made wrong but SAVEABLE: touch-up, re-welding, repainting, re-machining. Extra effort, but no replacement part is needed.
Enter it when there is a rework step. It is a separate section from Scrap because the two are mathematically different.
The “cost per repair” field takes either shape: a flat amount per repair, or the minutes spent plus a cost per minute. The second is closer to the truth when the repair is mostly a person's time, because then you can time it with a stopwatch instead of estimating it.
Worked example: 2,000 pieces a month, 3% need touching up, each touch-up costs 8,000 -> 2,000 x 0.03 x 8,000 = 480,000 a month. Nothing is grossed up, because those 60 pieces still ship; no replacement is made.
What does not belong here
- Parts scrapped outright - that is the Scrap category, and it has its own gross-up.
- Repair time you already folded into wages under Labor - entering it in both places counts it twice, and nothing warns you.
- The inspection effort that FINDS the defects - that is inspection time, and it belongs under Labor. This category counts only the repair.
- Penalties or customer compensation for late delivery caused by rework - that is a commercial consequence, not a cost of making one part.
Three common mistakes
| Mistake | What it does to the number |
|---|---|
| Folding rework into scrap to keep it simple | Cost comes out higher than it is, and any improvement to the defect rate looks like a bigger saving than it is |
| Folding repair time into Labor | Cost of quality disappears - “cost to make” and “cost to re-make” can no longer be read apart |
| Leaving it blank because “it is only a little” | A blank field is added as zero. For painting or welding this is rarely as small as it feels |
When it is worth separating this out
When you are arguing about whether to tighten incoming quality. Separate “cost to re-make” from “cost to make” and the two options separate themselves; nobody has to win the argument.
And when your improvement aims straight at the defect rate: this is the category where the number will move, and buried inside another one you will not see it move.
Try it on your own numbers, no sign-up: open the cost calculator and pick the Rework category.
Related guides
- The Ten Manufacturing Cost Categories, in Production Order
The ten cost categories Costdown uses to price a product — material, machinery, labor, tooling, scrap, rework, outsourced processing, packaging, logistics, factory overhead — with the formula and a worked example for each.
- How to Fill In the Before and After Cost Tables So the Saving Percentage Comes Out Right
How to enter each line in the current-state and optimized cost tables - item name, standard code, brand, monthly volume, cycle time - so the system computes the saving percentage, ROI and payback correctly.
More in this industry
- How to document a cost reduction project so other people trust it
- Is the saving real? Bottlenecks, and the three ways a number becomes money
- Six fields almost nobody fills in, and which way each one bends the cost
- Packaging Cost per Unit: Price It by Pack Quantity, Not by Weight
- Outsourced Processing Cost: Price per Part, and the Line Against Freight
- Allocating Factory Overhead Into Product Cost Without Counting It Twice
- Install and use a browser AI extension to write a Costdown proposal on your own
- What Is Cost Down? A Five-Stage Roadmap From the First Small Win to Cost Reduction as Daily Work
- Manufacturing cost formulas: two formulas, two different questions
What to do next
Now that you have read it, the fastest way to see your own numbers is to type them in. No account, nothing saved.
Rework Cost Calculator →And if reading this made you realise you have already done it: leave it here, and the next person is spared the road you already walked.
Publish a case →