Glossary · Quality & audit
AQL (acceptance quality limit) meaning
AQL stands for acceptance quality limit, often called acceptable quality limit: the worst defect rate tolerated when lots are judged on a sample.
What is the full form of AQL in quality?
In ISO 2859-1, AQL stands for acceptance quality limit. Older sampling standards called it acceptable quality level, and on Indian shop floors and in buyer contracts you will also hear acceptable quality limit; all three mean the same parameter. It is expressed as percent defective or defects per hundred units, and it comes from the attribute sampling tables in ISO 2859-1, which many Indian exporters, garment units and component suppliers inspect against.
How does AQL sampling work?
- Classify defects: buyers usually separate critical, major and minor defects and may set a different AQL for each, with critical defects often allowed none at all.
- Find the code letter: lot size and inspection level, commonly general level II, give a sample size code letter.
- Read the plan: the code letter and the AQL give the sample size, the acceptance number (Ac) and the rejection number (Re).
- Inspect and decide: pick the sample at random from the lot, count defectives, and accept the lot if the count is at or below Ac, reject it if it reaches Re.
What does an AQL decision look like? A worked example
Illustrative only; always read the current edition of the table your contract names. A lot of 2,000 pieces under general inspection level II falls in code letter K, which calls for a sample of 125 pieces. At an AQL of 2.5 for major defects, single sampling under normal inspection gives Ac 7 and Re 8.
| Majors found in 125 pieces | Decision |
|---|---|
| 0 to 7 | Accept the lot |
| 8 or more | Reject the lot |
Note what acceptance means. If 7 majors were found, the lot passes, yet the 1,875 pieces that were never opened may still hold defectives at a similar rate.
What do people get wrong about AQL?
- AQL is not a promised defect rate: a passed lot is not certified to be under 2.5 percent defective. AQL describes the sampling plan's behaviour over many lots, not the quality of one lot.
- AQL vs 100 percent inspection: sampling accepts or rejects lots; every-piece inspection accepts or rejects pieces. Our comparison of sample inspection vs every-piece photo QC sets out when each makes sense.
- Non-random samples: pulling the top cartons only tests the top cartons.
- Undefined defects: if the tolerance is not written down before inspection, inspector and supplier argue after it. A pre-dispatch inspection checklist fixes that.
Where a single wrong size reaching a customer costs more than inspecting every unit, brands move beyond sampling. With photo-evidence QC software such as Autowhat's AutoQC, a brand checks each piece with four photos measured against the spec, and a piece that has not passed cannot be packed or loaded.
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Where this shows up in our work. AutoQC: One barcode per piece, four measured photos against the spec, QA pass from anywhere. Book a 30-minute working session with an engineer.
Questions
What is the full form of AQL?
In ISO 2859-1, AQL stands for acceptance quality limit; it is also called acceptable quality limit or, in older standards, acceptable quality level. It is the worst average defect rate tolerated under sampling inspection.
What does AQL 2.5 mean?
AQL 2.5 means the sampling plan is designed around a tolerable process average of 2.5 percent defective. It sets the sample size and the number of defectives allowed before the lot is rejected.
Does passing AQL mean the lot has no defects?
No. A lot that passes AQL inspection can still contain defective pieces, because only a sample was checked. AQL controls the risk of accepting bad lots over time, not the content of one lot.