What AQL is
Acceptable Quality Limit is the worst defect rate a buyer will accept as an average across many shipments. It comes from ISO 2859-1, the international standard for inspecting goods by sampling rather than checking every piece.
Three kinds of defect
- Critical: unsafe or illegal, such as a needle left in a garment. Usually zero allowed.
- Major: likely to make a customer return the item, such as an open seam. Commonly AQL 2.5.
- Minor: a small flaw unlikely to cause a return, such as a loose thread. Commonly AQL 4.0.
How the sample is chosen
The lot size and the inspection level set a code letter, and the code letter sets the sample size. Most apparel inspections use General Inspection Level II.
| Lot size | Sample | Major, AQL 2.5 | Minor, AQL 4.0 |
|---|---|---|---|
| 501 to 1,200 | 80 | Accept 5, reject 6 | Accept 7, reject 8 |
| 1,201 to 3,200 | 125 | Accept 7, reject 8 | Accept 10, reject 11 |
| 3,201 to 10,000 | 200 | Accept 10, reject 11 | Accept 14, reject 15 |
Example: an order of 2,000 shirts means 125 shirts are checked. If 8 or more have major defects, the lot fails.
When to inspect
An inspection during production catches problems while they can still be fixed. A final random inspection is usually made once at least 80 percent of the order is packed.
Choosing your levels
A tighter AQL means a stricter inspection. Set it to match your price point and your customers’ expectations, write it into the purchase order, and make sure the supplier’s own quality team works to the same numbers.