AQL (Acceptance Quality Limit)
Understanding AQL (Acceptance Quality Limit)
A clear guide for importers and buyers
What is AQL?
AQL stands for Acceptance Quality Limit. It is defined in ISO 2859-1 as the quality level that is the worst tolerable process average when a continuing series of lots is submitted for acceptance sampling.
In simple terms, AQL tells you the maximum number of defects allowed in a random sample during quality inspection. If the defects in the sample are equal to or below the AQL limit, the entire batch is accepted. If exceeded, the batch is rejected.
Importers typically set different AQL values for three defect categories:
| Defect Type | Description | Examples |
|---|---|---|
| Critical | Defects that could cause safety hazards or make the product dangerous to use. | Sharp edges that can injure users, electrical faults, toxic materials. |
| Major | Defects that affect function, performance, or create obvious appearance issues. | Malfunctioning parts, large scratches, poor stitching, wrong dimensions. |
| Minor | Defects that do not affect function but may reduce customer satisfaction. | Small cosmetic marks, slight color variation, minor packaging flaws. |
How to Use AQL Tables
AQL inspection uses two standard tables from ISO 2859-1.
Table 1: Sample Size Code Letters (Full)
Find the code letter based on your lot size and inspection level. Most buyers use General Inspection Level II.
| Lot or Batch Size | S-1 | S-2 | S-3 | S-4 | I | II | III |
|---|---|---|---|---|---|---|---|
| 2 to 80 | A | A | A | A | A | B | C |
| 81 to 150 | A | A | A | A | A | B | C |
| 151 to 280 | B | B | B | B | B | C | D |
| 281 to 500 | B | B | B | B | B | C | D |
| 501 to 1,200 | B | C | C | C | C | D | E |
| 1,201 to 3,200 | C | D | E | G | H | K | L |
| 3,201 to 10,000 | C | D | F | G | J | L | M |
| 10,001 to 35,000 | C | D | F | H | K | M | N |
| 35,001 to 150,000 | D | E | G | J | L | N | P |
| 150,001 to 500,000 | D | E | G | J | M | P | Q |
| 500,001 and over | D | E | H | K | N | Q | R |
Table 2: Single Sampling Plan for Normal Inspection (Full)
Use the code letter from Table 1 to find the sample size and acceptable defect limits. AQL 2.5 (Major) and 4.0 (Minor) columns are highlighted for the example.
| Code Letter | Sample Size | AQL 2.5 | AQL 4.0 | Other AQL values* |
|---|---|---|---|---|
| A | 2 | 0/1 | 0/1 | — |
| B | 3 | 0/1 | 0/1 | — |
| C | 5 | 0/1 | 0/1 | — |
| D | 8 | 0/1 | 0/1 | — |
| E | 13 | 0/1 | 0/1 | — |
| F | 20 | 0/1 | 1/2 | — |
| G | 32 | 1/2 | 1/2 | — |
| H | 50 | 1/2 | 2/3 | — |
| J | 80 | 2/3 | 3/4 | — |
| K | 125 | 7/8 | 10/11 | — |
| L | 200 | 10/11 | 14/15 | — |
| M | 315 | 14/15 | 21/22 | — |
| N | 500 | 21/22 | — | — |
| P | 800 | — | — | — |
| Q | 1250 | — | — | — |
| R | 2000 | — | — | — |
* Other AQL values are shown in the original table (0.065 ~ 6.5). Only 2.5 and 4.0 are highlighted here for the example.
Example (3,000 vacuum cleaners)
Lot size: 3,000 → General Level II → Code Letter K
Sample size: 125 pieces
- Critical AQL 0 → 0 defects (1 or more = Fail)
- Major AQL 2.5 → ≤ 7 defects = Pass / ≥ 8 defects = Fail
- Minor AQL 4.0 → ≤ 10 defects = Pass / ≥ 11 defects = Fail
If any limit is exceeded in the 125-piece sample, the entire lot fails inspection.
I hope this guide helps you better understand AQL and quality control for your imports.
Feel free to leave a comment if you have any questions!
