Defective Rate Calculator
What is a Defective Rate?
The defective rate, often referred to as the failure rate or defect density, is a critical Key Performance Indicator (KPI) in manufacturing and quality assurance. It represents the percentage of output that fails to meet quality standards compared to the total output produced. Monitoring this metric allows businesses to identify inefficiencies in production lines, supply chain issues, or training gaps.
How to Calculate Defective Rate
The formula for calculating the defective rate is straightforward:
Defect Rate (%) = (Number of Defective Units / Total Units Produced) × 100
To calculate the Yield Rate (the percentage of good units), use the inverse formula:
Yield Rate (%) = 100% – Defect Rate (%)
Example Calculation
Suppose a factory produces 10,000 widgets in a single shift. Upon inspection, quality control finds that 150 widgets have flaws.
- Total Units: 10,000
- Defective Units: 150
- Calculation: (150 / 10,000) × 100 = 1.5%
The defect rate is 1.5%, meaning the yield rate is 98.5%.
Understanding DPMO (Defects Per Million Opportunities)
In Six Sigma and high-precision manufacturing, percentages can sometimes be too broad. Instead, companies use DPMO or PPM (Parts Per Million). This metric extrapolates the current defect rate to a theoretical production run of one million units.
Formula: (Defective Units / Total Units) × 1,000,000
Using the example above: (150 / 10,000) × 1,000,000 = 15,000 PPM.
Why Monitoring Defect Rates Matters
- Cost Reduction: Defective products result in wasted raw materials, energy, and labor.
- Customer Satisfaction: High defect rates increase the likelihood of bad products reaching the customer, leading to returns and reputation damage.
- Process Improvement: A rising defect rate acts as an early warning system for equipment failure or process drift.