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What does AQL 2.5 mean ?

AQL 2.5

The term “AQL 2.5” forms part of hundreds of purchase orders sent to Chinese manufacturers however what does AQL 2.5 mean? Buyers and suppliers understand and agree that it is some kind of tool to measure the quality during a pre-shipment inspection. While this is true, buyers, suppliers and third party inspection companies may interpret it differently therefore more precise information are required to avoid misunderstandings.


What does AQL 2.5 mean?

In the strict sense of the term, “AQL 2.5” is a partial application of the ISO 2859-1 standard, which is also copied in other normative bodies such as ANSI: “The acceptable quality limit (AQL) is the worst tolerable process average (mean) in percentage or ratio that is still considered acceptable; that is, it is at an acceptable quality level.

AQL 2.5 means the buyer considers as acceptable quality limit a defect rate of 2.5% of the total order quantity.

Defects classification and acceptable quality limit

In the quality control industry, defects are classified per critical, major and minor. If the buyer only mentions AQL 2.5, it means that the buyer accepts all kind of defects: critical, major or minor, to be present in the manufactured goods at a level of 2.5% of the total order quantity. Knowing that a critical defect is dangerous for the user, it is quite risky for the buyer to include in the 2.5% such defect type.

It is highly recommended to define an acceptable quality limit for each defect type: critical, major, minor.

Other interpretations are possible such as: considering that the AQL standard applied in the quality control industry is AQL 0 for critical defects, AQL 2.5 for major defects and AQL 4.0 for minor defects. However without those details, the supplier and the Quality Control company may consider the client only require a limit on major defects and no limits on minor defects or critical defects.

Need of precise instructions about the Acceptable Quality Limits

Just stating “AQL 2.5” without any further information is definitely not enough. Buyers should clearly define its acceptable quality limits per defect types in order to avoid any misunderstanding.

In addition, it is also necessary to define the AQL sample size, the defect category definitions (if different from the standard one used by third party inspection companies), the tolerances if required, etc.

And you: how do you mention your acceptable quality limits to your supplier and quality control partner?


AQF Quality team

We ensure service quality and reliability by improving the performance of our processes. We follow up and train inspectors and supervisors to enhance their skills and meet the latest regulations and standards. In the Quality Control Blog we write about the industry changes and provide solutions for a better Quality Control management in Asia. For more information.

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12 responses to “What does AQL 2.5 mean ?”

  1. harish dubey says:

    what is aql calculation

  2. anix says:

    how we can differ minor into major and major into critical?
    how much minor unit equal to 01 major?
    how much major unit equal to 01 critical?

  3. anix says:

    what should be packing percentage at AQL normal level at 1.5/2.5/4.0 ?
    how much part should be packed of total quanity at the time of inspection, whether it is 70%/80% or any different percentage.

    • mm Claire Piccinno says:

      @Anix: thank you for your comment and questions which may help many other buyers! If you are checking the goods before shipment, then we highly recommend to ensure 100% of your goods are produced and 80% are packed in export cartons. You can find a very interesting article that explains the reasons here. For other type of inspections, it depends on your expectations of finished and packed goods. Feel free to contact us should you need a more personalized answer, taking into account your requirements and product specifications.

    • anix says:

      @Claire: Thanks for your cooperation, I’ve been benefited to get this information by you side.
      Additionally, for the more personalized answer it is to ask you that what are the minor, major and critical fault/problems in the soccer ball (football) products. How we can differ or declare minor, major and critical problems in soccer ball during inspection? picture with information may most benefited for our better understanding as a entire QA & Production Team.

    • mm Claire Piccinno says:

      @Anis: this differs a lot depending on the customer as quality requirements vary based on the market, the use of the product, etc. We do have a standard rule set up but always welcome our clients to an open discussion on that topic. Feel free to contact us so that we can define the best criteria together with you.

  4. Mark says:

    @ Lian. Thanks for your reply. As a buying office we deal with these questions a lot from customers. The problem is to explain why the inspection table allows 5-6% but in the then it should come out as 2.5% overall based on the probable function. We have had cases where customers checked 100% at destination and the result came out to be exactly the same percentage as the AQL table in the inspection allowed. It is an important issue for importers to calculate possible wastage into their prices … If they use and 2.5/4.0 Major/Minor, which percentage would you suggest an importer to expect as maximum defect ? 2.5 + 4.0 = 6.5% of the total quantity ?

    • @Mark: Thanks for your interest regarding this topic. Actually when performing an inspection (the inspected sample size is determined according AQL table), the defect rate may be different of the total quantity defect rate. Since AQL standards take into account the probability of having more defective products than the overall defect rate.
      Lets take an example: On a production of 100 pieces we have in total 20 pieces that are defective.
      – If we take a sample size of 10 pieces for inspection, we may have 3 or 4 defective pieces from this inspected sample size.
      – However it doesn’t mean that the defect rate of this sample size correspond to 30% or 40% of the total quantity.
      – To avoid any misunderstanding it is important to clearly separate the defect rate of the total quantity and the defect rate of the inspected sample size.
      – AQL standard does take into account those 2 values but it remains statistical. Therefore it is not 100% accurate.
      – The only way to know the total quantity defect rate is to check the total quantity of the order.
      Hope this explaination will help you to answer to your customers. You could also invite them to check articles from Quality Control Blog

  5. Mark says:

    “AQL 2.5 means the buyer considers as acceptable quality limit a defect rate of 2.5% of the total order quantity.”
    I dont think this is true ;-) If you look at any AQL table, f.e. a Normal Level II single at lets say 15000 pcs order qty it will give you a sample size of 315 with 14/15 defective as limit = approx. 5%. If this is a major level and you add an AQL 4.0 as minor level you may end up with an acceptable defective limit of 10% and more…


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