What is defect density?

Defect density is the number of defects per square inch of product. It can be a valuable measurement for manufacturers, especially when tracking down problems in their manufacturing lines.

How is defect density measured?

Defect density is often expressed as the number of defects per unit of product. For example, if you have one product with 100 defects and another with 200, the first one will have a higher defect density than the second.

Defect density can be measured in many ways:

  • Defects per KLOC (kilocycles of logic)
  • Defective lines of code (LOC) per thousand lines of code (KLOC), which is also known as FxLOC
  • Line fault density (LFD) or line fault frequency (LFF)

What is the defect density formula?

Defect density is the number of defects per unit. It's measured in parts per million (ppm). The formula for calculating defect density is:

Defect density


Total number of defects   ÷

Total units produced

Suppose you have 1,000 defective units and made 50,000 units in total. Your defect density would be 0.02. If you multiply this by 100%, you get your defect density as a percentage, which will be 2%.

What is a good defect density in manufacturing?

Generally speaking, a good defect density falls within the following parameters:

  • It is less than 1 defects per thousand
  • It is less than 1.5 defects per thousand
  • It is less than 0.5 defects per million

Although these are considered good in manufacturing, some manufacturers have stricter parameters.

How do you reduce defect density?

You can reduce defect density by implementing:

  • Statistical process control (SPC): SPC is a technique that uses statistical methods to monitor processes and detect when they are performing outside of their control limits. It can help you identify the cause of defects in your product or service, allowing you to take steps toward reducing them.
  • A process improvement team: A group of people who improve existing processes can significantly reduce defect density. They'll work together as a team, share ideas and discuss potential solutions until they reach a consensus on how best to improve things.
  • The six sigma approach: This methodology focuses on reducing variation in manufacturing processes by eliminating waste from them through analysis and optimization techniques such as DMAIC—define, measure, analyze, and improve/control (or define, measure, etc.). The goal here is for every employee at every level within an organization (including top management) to understand how each part contributes towards improving overall quality performance across all departments. This is done so there's no room left for confusion about where improvements need to be made or why changes were made after implementation takes place.

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What are the benefits of measuring defect density?

There are several benefits to measuring defect density. Here are some notable examples:

  • Improved quality: the quality of your products goes up as you make changes to reduce defects.
  • Lower costs: you’re spending less time on waste and are focused on optimizing techniques. This gives your team time to focus on other pertinent parts in the business.
  • Improved customer satisfaction: if your defect density is lowered, your customers may receive larger shipments of products faster.
  • Increased employee morale: if the defect density is lowered, your team KPIs are better, and that takes performance pressure off of your team.

A low defect density can help improve efficiency, quality, and customer satisfaction

You can use a defect density analysis to measure your company's quality, efficiency, and customer satisfaction. The key is to know what the correct numbers are so that you can make improvements when necessary.

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