Defect Rate (Parts Per Million)
PPM) – number of defective units produced per million units
What is Defect Rate (Parts Per Million)?
Defect rate in parts per million (ppm) is the number of defective units per million produced. It is a precise way to express quality in high-volume manufacturing.
When defect levels are very low, ppm shows differences that percentages hide.
How this KPI is measured
- Function
- Operations & Supply Chain
- Sub-function
- Quality Control
- Industry
- Manufacturing
- Type
- Lagging
- Impact
- Quality
- Unit
- ppm
- Measurement frequency
- Daily / Weekly
- Formula
- (Defective units / Total units produced) × 1,000,000
How to calculate it
Divide defective units by total units produced, and multiply by 1,000,000.
For example, if 45 of 300,000 units were defective, the rate is (45 / 300,000) x 1,000,000 = 150 ppm.
Define a defect clearly, and measure at the same point in the process each time, for example at final inspection or as returned by customers.
Where it is used
Tracking quality
Follow defect levels.
Managing suppliers and customers
Agree quality limits.
Driving improvement
Set targets.
How to improve it
Tips and common mistakes
- Small sample sizes make ppm unreliable.
- Track internal and customer-found defects separately.
- Use consistent definitions.
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