Manufacturing Scrap Rate Calculator
Calculation Results
How to Calculate Scrap Rate Percentage
Calculating scrap rate is a fundamental practice in manufacturing quality control. It measures the efficiency of a production process by quantifying the percentage of materials or parts that fail to meet quality standards and must be discarded or reworked. A high scrap rate indicates inefficiencies, equipment issues, or raw material problems, directly impacting the bottom line.
The Scrap Rate Formula
The formula to calculate scrap rate is straightforward. It is the ratio of defective parts to the total number of parts produced, expressed as a percentage:
Scrap Rate = (Total Scrap Parts ÷ Total Parts Produced) × 100
For example, if a factory produces 5,000 widgets and 200 are rejected during quality control, the calculation would be: (200 ÷ 5,000) × 100 = 4%.
Why Monitoring Scrap Rate is Critical
- Cost Reduction: Every scrapped part represents wasted raw materials, energy, and labor.
- Process Improvement: Tracking this metric helps identify specific shifts, machines, or materials causing defects.
- Yield Optimization: The inverse of scrap rate is the yield rate (the percentage of good parts). Improving yield directly increases saleable inventory without increasing production volume.
Scrap Rate vs. Yield Rate
While scrap rate focuses on waste, First Pass Yield (FPY) focuses on success. They are inversely related. If your scrap rate is 3.5%, your yield rate is 96.5%. Most Lean Manufacturing and Six Sigma initiatives aim to reduce scrap rates to near zero (or 3.4 defects per million opportunities in Six Sigma).
Calculating the Cost of Scrap
To understand the financial impact, you must multiply the number of scrapped units by the cost per unit. This calculator includes a field for "Cost Per Part" to help you estimate the total financial loss associated with the current defect rate. Note that this often underestimates the true cost, as it may not include disposal fees or the opportunity cost of lost machine time.