Acceptable Quality Limit (AQL) is the cornerstone of modern product inspection. Developed from MIL-STD-105E and now standardized as ISO 2859-1, AQL provides a statistically valid method for determining how many units to inspect and how many defects are acceptable.
How AQL Tables Work
The AQL system uses three inputs: lot size (total batch quantity), inspection level (usually General Level II), and AQL percentage (typically 0, 2.5, or 4.0). These three variables determine your sample size and acceptance/rejection numbers.
For example, with a lot of 5,000 units at General Level II, the sample size code letter is "L". At AQL 2.5, you inspect 200 units. If you find 10 or fewer major defects, the lot passes. At AQL 4.0, the same 200 units allow up to 14 defects.
Choosing the Right AQL Level
Most importers use AQL 2.5 for major defects and AQL 4.0 for minor defects. Critical defects (safety issues) typically use AQL 0 — meaning zero critical defects are allowed. Some retailers like Walmart require AQL 1.0 or stricter.
Real-World Application
In a recent textile inspection in Bangladesh, we applied AQL 2.5/4.0 to a 3,000-piece garment shipment. Sample size: 200 units. We found 8 major defects (stitching issues) and 12 minor defects (loose threads). Result: PASS at both AQL levels. The shipment proceeded, and the buyer received quality goods.
Common Mistakes to Avoid
Never change AQL levels mid-inspection. Don't combine different product types into one lot — each SKU needs separate sampling. Always use the actual lot size, not the order quantity. And remember: AQL is about lot acceptance, not individual unit quality.