Acceptable Quality Limit (AQL) is a statistical sampling method used in pre-shipment inspection, based on standards such as ANSI/ASQ Z1.4 and ISO 2859-1. Instead of checking every unit, the inspector draws a sample and compares the defects found to an agreed limit.

AQL is expressed per defect class. A common level is AQL 2.5 major / 4.0 minor, meaning the sample may contain up to a set proportion of major and minor defects and still pass. Critical defects, such as safety hazards, are usually set to zero.

The buyer defines the AQL in the inspection brief. The level you choose balances cost and risk: a tighter AQL with lower numbers rejects more lots, while a looser level accepts more variation. A level like 2.5 major / 4.0 minor is a common starting point, but you can tighten or loosen it by product and market.

Practical takeaway: Put the AQL levels and defect classification in your inspection brief so the inspector and the factory work to the same acceptance standard.