In sampling plans such as ISO 2859-1, the acceptance quality limit, or AQL, is the quality level the plan is designed around for a series of lots. Together with the lot size and the inspection level, it determines the sample size and how many defective units are allowed in the sample before the lot is rejected. A lower AQL number means a stricter plan. It does not mean the lot may contain exactly that percentage of defects; it describes how the sampling plan is likely to treat lots of different quality.

Define the defect classes first

The AQL only works if everyone agrees what counts as critical, major and minor. A critical defect could make the product unsafe or illegal to sell, such as a broken needle or a drawstring on a small child's hood. A major defect would likely lead to a return, such as a hole, a wrong size or a stain on the front. A minor defect is a small departure that most customers would not return the item for. Write a defect list with examples for your products and attach it to the inspection booking.

Choosing the levels

Many buyers allow no critical defects at all, use a stricter AQL for major defects than for minor ones, and adjust based on product value and the risk of returns. A premium line or a first order with a new factory may justify a stricter major level. Whatever you choose, use the same levels across inspections so results can be compared.

Name the edition and inspection level

ISO 2859-1 was revised in 2026, so state the edition in the purchase order. Also state the inspection level, since it changes the sample size. General inspection level II is a common default in sampling tables.

Add measured checks

AQL sampling covers defects found by visual and functional checks. Measurements such as shrinkage after a named wash procedure such as ISO 6330, or fabric weight under ASTM D3776, need their own sampling rules and pass limits.

Review results over several orders. If one defect type keeps appearing, fix it at source rather than relying on the AQL to catch it.