A 3% defect rate sounds small until it is 30 rejected pieces in a 1,000-piece export order, a returned batch of 200 boxes of sweets, or a marketplace account suspended for returns. Defect rate is the share of output that fails inspection or is returned as faulty; yield is its mirror. This calculator computes defect rate, first-pass yield and DPMO (defects per million opportunities) from your inspection counts, estimates the cost of quality — rework, scrap, returns — and tracks it by batch, line, supplier or shift so the cause shows itself.
The formulas
- Defect rate = Defective units ÷ Units produced (or inspected) × 100.
- First-pass yield = Units passing without rework ÷ Units started × 100.
- DPMO = Defects ÷ (Units × Opportunities per unit) × 1,000,000 — for products with several checkpoints.
- Cost of poor quality = Scrap × unit cost + Rework × rework cost + Returns × return cost.
A batch of 2,400 shirts had 84 rejected at final inspection and 110 reworked → defect rate 3.5%, first-pass yield 91.9%. With 6 inspection points per shirt, 240 total defects gives a DPMO of 16,667 — about a 3.6-sigma process. At ₹220 per scrapped shirt and ₹35 per rework, the batch cost ₹22,330 in quality losses.
How to use the calculator
- Enter units produced or inspected, defective units, and (optionally) reworked units and the number of defects.
- Enter opportunities per unit if you want DPMO and sigma level.
- Enter unit cost, rework cost and return cost to see the cost of poor quality.
- Tag results by batch, supplier, machine, shift or operator and compare.
- Track weekly; set a target and alert threshold (for example 2% target, 4% alert).
Where defects come from
| Symptom | Likely cause | Where to look |
|---|---|---|
| Defects concentrated in one shift | Training, fatigue, supervision | Capacity utilisation — is the shift overloaded? |
| Defects rise with a new supplier lot | Input quality | Incoming inspection; note it on the purchase order terms |
| Defects found only by customers | Weak final inspection | Add a checkpoint; track order accuracy and returns |
| Damage in transit | Packaging | Box size and cushioning — the volumetric weight trade-off |
| Random, low-level defects | Process variation | Standard work, jigs, calibrated tools |
Quality and the customer
Marketplaces measure "return due to defect" and suspend listings above roughly 1–2%; B2B buyers specify AQL (acceptable quality levels) in the PO and reject whole lots above it. A supplier's credit note for rejected goods and the buyer's debit note follow. For food businesses, defect control includes labelling and hygiene under FSSAI — see FSSAI rules for small food businesses.
Reducing the rate
- Inspect early (incoming and in-process), not only at the end; a defect caught at cutting costs ₹5, at packing ₹220.
- Write a one-page standard for each operation with a photo of "good" and "not good".
- Track the top three defect types and fix the biggest first — 60–70% of defects usually have one or two causes.
- Reward first-pass yield, not just output.
- Re-measure after every change; the trend line is the proof.
Related tools
- Order accuracy — fulfilment errors downstream of production.
- Capacity utilisation — overloaded lines make more defects.
- Credit note — for goods rejected by customers.
- Purchase order — put AQL terms on supplier orders.
- Gross margin calculator — the margin quality losses eat into.
- Capacity utilisation — overloaded lines make more defects.