AQL stands for acceptable quality limit. In an AQL inspection in India, the inspector draws a random sample from the lot, counts the defects, and passes or fails the whole lot depending on whether the count stays within a limit you set in advance. The method is defined in the sampling standard ISO 2859-1.
It is a sampling system, not a guarantee. Passing means the lot is probably within your limit, not that every unit is perfect. If your product is safety-critical, you want a much stricter plan or a full check.
The three decisions you make
- The inspection level, which together with lot size sets the sample size. General level II is the usual default; level III means a larger sample and level I a smaller one.
- The AQL value for each defect class, a number such as 2.5 or 4.0 that controls how many defects are tolerated.
- The defect classes: critical, major and minor, each defined with examples before the inspection.
The common starting point
Many importers of consumer goods use level II with no critical defects tolerated, an AQL of 2.5 for major defects and 4.0 for minor defects. Stricter products such as medical or children's goods usually go tighter. Cheaper decorative goods sometimes go looser. There is no universal right answer, and the right level depends on the damage a defect would do to your business.
A worked example
Take a lot of 5,000 units under general level II. The standard's tables give a code letter L, which means a sample of 200 units. With an AQL of 2.5 for major defects, the lot passes if 10 or fewer major defects are found and fails at 11. With an AQL of 4.0 for minor defects, it passes at 14 or fewer and fails at 15. Any critical defect fails the lot. The sample is a fraction of the lot, so a pass is a statement about probability, and a fail on the sample is a fail for the whole lot, not only for the cartons that were opened. Check the exact figures against the tables in the standard or with your inspector, because they change with lot size.
Now suppose the inspector finds 8 major and 16 minor defects. The major count is within the limit, but the minor count is over. The lot fails on minor defects. Whether you then reject it, sort it or accept it with a concession is a commercial decision, which is why you agree the response before inspection. A common rule is that a failed lot is sorted or reworked by the factory at its own cost and presented again for a second inspection, usually at a tighter sample size, with the cost of the second visit falling on the supplier.
Mistakes to avoid
- Not defining the defects. AQL counts what the inspector decides is a defect, so write the defect list and attach photos.
- Letting the factory pick the cartons. Selection must be random across the whole lot.
- Inspecting before the lot is complete, which makes the sample meaningless.
- Mixing products or batches in one lot, so a good batch hides a bad one.
- Treating a pass as proof of safety or legal compliance. AQL checks appearance and function, not lab results.
- Setting AQL tight on minor points and forgetting the important ones, such as strength or material.
Product-specific guidance
Practice varies with the product. See AQL for tile inspection, AQL for jewellery inspection, garment AQL levels explained and AQL for engineering components. For measured parts, see how dimensional inspection sample size works.
When AQL is the wrong tool
Some products and risks do not suit sampling. For safety-critical parts, high-value single items or goods where one defect is serious, a full check of every unit may be the right approach. Food safety, contamination and compliance with legal limits are matters for laboratory testing, not visual sampling.
A sampling plan also assumes a uniform lot. If a lot is made of several batches, shifts or materials, ask the inspector to sample each separately or to treat them as separate lots. Otherwise the average hides the weak part, and a pass tells you less than you think.
How we work
We set the level and the defect list with you before production, and we inspect against them, taking sealed counter-samples from the lot. The levels in your contract should be the ones the inspector uses. To agree them for your product, book a free sourcing review.