What is AQL (Acceptance quality limit)?

AQL sampling comes from ISO 2859-1 and its US equivalent, ANSI/ASQ Z1.4. Based on the lot size and an inspection level (General Level II is the usual default), the tables give a sample size and the maximum number of defects allowed before the lot is rejected.

Defects are classed by severity. A common setting for consumer and commercial goods is zero tolerance for critical defects (safety hazards), 2.5 for major defects and 4.0 for minor defects, but each buyer sets its own levels. A lower AQL number means a stricter inspection.

AQL is a sampling plan, not a promise that every unit is perfect. Agree the AQL levels, the defect list and the checks on function, dimensions and packing with the factory before production, so the result is not up for debate.

Read next

• Quality inspection