What Is Rework Rate?
Rework Rate measures the proportion of production that requires additional processing to meet specifications. Unlike scrap, reworked items are recoverable — but the additional labour, machine time, and material consumed represent hidden cost and lost capacity.
This is the “hidden factory” — the work being done that produces no additional output.
The Formula
Rework Rate = (Reworked Units ÷ Total Units Produced) × 100%Data Requirements
| Source | Required | What You Need |
|---|---|---|
| Machine Data | Yes | Production count, rework count |
| MES | Optional | Rework reason codes and tracking |
Rework Rate is a Phase 2 metric — it can be calculated from basic production data.
Why It Matters
- Hidden capacity loss — rework consumes capacity that could produce new output
- Process capability — high rework indicates an inconsistent process that can produce good parts but doesn’t do so reliably
- Cost — rework labour and materials add cost without adding revenue
- Quality system indicator — rework means defects are being caught (good) but not prevented (needs improvement)
Common Pitfalls
- Not tracking all rework — minor touch-ups and adjustments are often unreported
- Not recording rework reasons — without root cause data, improvement is guesswork
- Counting reworked parts as first-pass good in FPY calculations — they should not be
Best Practices
- Classify rework by severity (minor adjustment vs major reprocessing)
- Track rework reason codes to guide process improvement
- Calculate the full cost of rework (labour + materials + lost capacity)
- Focus on prevention rather than perfecting the rework process
- Use rework data to prioritise process improvement projects
Related Metrics
- First Pass Yield — rework reduces FPY even though the product eventually ships
- Scrap Rate — the unrecoverable counterpart to rework
- Defect Rate — rework is a response to defects
- Cycle Time — rework extends effective cycle time