Defect Analysis Tool Calculator

Example Data Table

Formula Used

• Defect rate (%) = (Defective units ÷ Units inspected) × 100
• Yield (%) = ((Units inspected − Defective units) ÷ Units inspected) × 100
• DPU = Total defects ÷ Units inspected
• DPO = Total defects ÷ (Units inspected × Opportunities per unit)
• DPMO = DPO × 1,000,000
• Sigma ≈ InvNorm(1 − DPMO/1,000,000) + 1.5
• Severity index = (3×Critical + 2×Major + 1×Minor) ÷ Total defects
• COPQ = (Total defects×Rework) + (Defective units×Scrap) + (Inspection hours×Labor rate)

How to Use This Calculator

1. Enter the inspection totals: units inspected, defective units, and total defects.
2. Set opportunities per unit based on your checkpoints or CTQs.
3. Optionally add critical, major, and minor counts for severity tracking.
4. Optionally enter cost inputs to estimate the cost of poor quality.
5. Add defect types and counts to generate a Pareto view.
6. Press Submit; results appear above the form, under the header.
7. Use the export buttons to save a CSV or PDF summary.

Defect rates and yield baselines

Defect rate tracks the share of units that fail inspection, while yield reports the pass share. Start by trending both weekly, using the same sampling plan and lot definition. A stable process shows narrow swings; sudden jumps usually indicate a material, method, or operator change. If defect rate is 2.4% on 1,000 units, yield is 97.6%, which sets a clear baseline for improvement. Document the baseline with run charts, and review it in daily huddles to keep attention on variation.

DPU, DPO, and DPMO interpretation

DPU measures how many defects occur per unit, capturing repeated issues on the same item. DPO normalizes defects against the number of opportunities, which is essential when products have multiple checkpoints. DPMO scales DPO to one million opportunities, enabling comparisons across lines. For example, 37 defects with 1,000 units and 10 opportunities gives DPO 0.0037 and DPMO 3,700.

Sigma level and process capability signals

The tool estimates sigma from the defect probability and adds a conventional 1.5 sigma shift for long‑term drift. Higher sigma implies fewer defects and stronger process control, but it should be compared to real capability studies when available. Treat sigma as a screening metric: use it to rank processes, then validate root causes with SPC charts and measurement system checks.

Pareto focus and corrective action routing

Defect logs are converted into a Pareto distribution so teams can focus on the “vital few” categories that create most losses. When one defect type represents 40% of all defects, addressing it often yields faster gains than small, scattered fixes. Pair each top category with a containment action, an owner, and a due date, then verify results with the next inspection cycle.

Cost of poor quality and prevention levers

COPQ combines rework, scrap, and inspection labor to translate defects into money. Use it to justify prevention work such as poka‑yoke, training, fixture upgrades, or supplier tightening. If rework is 1.50 per defect, scrap is 12.00 per defective unit, and inspection is 6 hours at 8.00, the tool quantifies the total impact and highlights where the biggest savings sit.

FAQs

1) What is the difference between defective units and total defects?

Defective units counts how many items failed at least one check. Total defects counts every defect found, including multiple defects on one unit.

2) How do I choose opportunities per unit?

Use the number of independent defect opportunities per unit, such as inspection checkpoints or critical-to-quality characteristics. Keep it consistent over time so DPMO trends remain comparable.

3) Why does the sigma estimate include a 1.5 shift?

The 1.5 shift is a conventional long-term adjustment used in Six Sigma reporting to account for process drift. It helps compare performance across processes, but it is not a substitute for capability studies.

4) What does the severity index tell me?

It summarizes defect mix using weighted counts (critical, major, minor). A higher value means defects are more serious on average, even if the total defect count stays similar.

5) How should I use the Pareto results?

Focus improvement on the top categories that contribute most defects. Assign ownership, confirm causes, implement countermeasures, and then validate with the next sampling cycle.

6) Which costs belong in COPQ for this tool?

Include direct rework cost per defect, scrap cost per defective unit, and inspection labor. You can also track warranty or downtime separately, then add them to COPQ reporting if you have reliable data.