Six Sigma uses many terminologies. Six Sigma is often referred to as normal distribution, DMAIC and FMEA. Six Sigma is about optimizing or improving processes to minimize defects. Defects per Unit (DPU) is a key term in Six Sigma. Green Belt Certification requires knowledge of terms such as DPU. There are free online Six Sigma courses as well as free Lean Six Sigma training that can help clarify any confusion.
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This article will explore the DPU and its role in Six Sigma.
We will be discussing the following points one by one about DPU metric.
Six Sigma defines the word “Defect”
What is Defects per unit (DPU)?
Three steps to calculate the Defects per Unit (DPU).
Defects per Unit (Formula & Illustration)

What is Six Sigma’s definition of “Defect”?
Before we get to the DPU metric, let’s first define what the term ‘Defect’ means in Six Sigma methodology. Six Sigma-DMAIC-based projects often include defects as a key component. This is because the goal of many Six Sigma projects is to improve customer satisfaction and process performance by reducing defect rates. Each defect must meet at least one of the S-M-A-R-T criteria.
“Anything that is not in accordance with customer specifications” is a defect. A defect is a situation or transaction that does NOT meet customer requirements. A defect can also be defined as a failure of the customer to meet their quality expectations. Six Sigma’s central principle is that quality is defined by the customer. The customer defines quality.
A tailored shirt or trouser that is either too long or too short is an example of a defect. This is contrary to the customer’s request and would be considered a defect. A defect is a pizza delivery that takes too long. A defect is a DTH service that has an inaccessible channel. One caveat: The existence of one or more defects within a process, product, or service does not necessarily indicate that the product or process is defective. Six Sigma terminology defines a defect as the failure of the entire process, product, or service. A defect is a small dent on the body of a car that’s just arrived in the showroom. If one or more customers refuses to purchase the car due to this defect, it will be considered defective.

What are Unit Defects?
DPU is a measure that shows how well your product or process performs based on the number and severity of defects. DPU is the average number of defects per unit of product or service. DPU is the average number of defective units per sampled unit. Don’t forget to quantify the defects being considered for this metric.
Let’s also look at Six Sigma’s definition of the term “Unit”. A unit is an item in process. Each unit is either defective or undefective according to DPU. This refers to units with one or more defects.
How do you calculate DPU?
Let’s now take a look at the three steps required to calculate the DPU.
The first step is to determine how many units you will sample. This is the size of the sample. The sample size should be small enough that it is manageable but large enough to reflect the problem.
The second step is to count how many defects or errors are found in the sample. This means that you will need to count the number of units in the sample group that contain at least one defect.
The third step returns the DPU as an integer number that can be converted into a percentage.
Let’s look at a qu