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What Is an Acceptable Quality Level (AQL)?
The acceptable quality level (AQL) is a crucial measure used in product inspections to determine the maximum number of acceptable defects in a sample size before a batch is rejected. It is usually expressed as a percentage or ratio, indicating the number of defects compared to the total quantity. Importers typically set different AQLs for critical, major, and minor defects to maintain high-quality standards.
The acceptable quality level (AQL) represents the worst quality level tolerable for a product.
AQL varies by product, with items posing higher health risks having lower AQLs.
Setting appropriate AQLs ensures product quality and compliance with safety regulations.
How Do I Determine the Right Sample Size and Acceptance Number?
Determining the right sample size and acceptance number involves agreeing on an AQL standard suitable for the level of risk both buyers and sellers are willing to assume. This standard is used during pre-shipment inspections and is essential for quality control. Common settings for consumer goods in China include:
- 0% for critical defects (unacceptable as they may harm users or violate regulations).
- 2.5% for major defects (unacceptable to most end users).
- 4.0% for minor defects (minor deviations from specifications that most users would tolerate).
AQL Calculator
Based on the Tables
For a batch to pass inspection based on the AQL Tables, the inspector must select a sample of items and meet the following criteria:
Major defects are found on a maximum of sample(s).
Minor defects are found on a maximum of sample(s).
Table I - Sample size code letters
| Lot or Batch Size | Normal Inspection Levels | Special Inspection Levels | |||||
|---|---|---|---|---|---|---|---|
| I | II | III | S1 | S2 | S3 | S4 | |
| 2 to 8 | A | A | B | A | A | A | A |
| 9 to 15 | A | B | C | A | A | A | A |
| 16 to 25 | B | C | D | A | A | D | D |
| 26 to 50 | C | D | E | A | B | B | C |
| 51 to 90 | C | E | F | B | B | C | C |
| 91 to 150 | D | F | G | B | B | C | D |
| 151 to 280 | E | G | H | B | C | D | E |
| 281 to 500 | F | H | J | B | C | D | E |
| 501 to 1,200 | G | J | K | C | C | E | F |
| 1,201 to 3200 | H | K | L | C | D | E | G |
| 3,201 to 10,000 | J | L | M | C | D | F | G |
| 10,001 to 35,000 | K | M | N | C | D | F | H |
| 35,001 to 150,000 | L | N | P | D | E | G | J |
| 150,001 to 500,000 | M | P | Q | D | E | G | J |
| 500,001 and over | N | Q | R | D | E | H | K |
How to Read the AQL Table?
Reading the AQL table involves two primary tables. The first table helps determine the 'code letter' based on the lot size and inspection level. This code letter then indicates the sample size and the maximum number of acceptable defects.
Table II - Single sample plans for normal inspection (Master Table)
| Sample Size Code Letter | Sample Size | Acceptable Quality Levels (Normal ispection) | |||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.065 | 0.10 | 0.15 | 0.25 | 0.4 | 0.65 | 1.0 | 1.5 | 2.5 | 4.0 | 6.5 | 10 | ||||||||||||||
| Ac | Re | Ac | Re | Ac | Re | Ac | Re | Ac | Re | Ac | Re | Ac | Re | Ac | Re | Ac | Re | Ac | Re | Ac | Re | Ac | Re | ||
| A | 2 | 0 | 1 | ||||||||||||||||||||||
| B | 3 | 0 | 1 | ||||||||||||||||||||||
| C | 5 | 0 | 1 | 1 | 2 | ||||||||||||||||||||
| D | 8 | 0 | 1 | 1 | 2 | 2 | 3 | ||||||||||||||||||
| E | 13 | 0 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | ||||||||||||||||
| F | 20 | 0 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 5 | 6 | ||||||||||||||
| G | 32 | 0 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 5 | 6 | 7 | 8 | ||||||||||||
| H | 50 | 0 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | ||||||||||
| J | 80 | 0 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | 14 | 15 | ||||||||
| K | 125 | 0 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | 14 | 15 | 21 | 22 | ||||||
| L | 200 | 0 | 1 | 1 | 2 | 2 | 3 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | 14 | 15 | 21 | 22 | ||||||
| M | 315 | 1 | 2 | 2 | 3 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | 14 | 15 | 21 | 22 | ||||||||
| N | 500 | 1 | 2 | 2 | 3 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | 14 | 15 | 21 | 22 | ||||||||
| P | 800 | 1 | 2 | 2 | 3 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | 14 | 15 | 21 | 22 | ||||||||
| Q | 1250 | 2 | 3 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | 14 | 15 | 21 | 22 | ||||||||||
| R | 2000 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 11 | 14 | 15 | 21 | 22 | ||||||||||||
| Use first sampling plan below arrow. if sample size equals or exceeds lot size, carry out 100% inspection | |||||||||||||||||||||||||
| Use first sampling plan above arrow | |||||||||||||||||||||||||
| Ac: Acceptance number | |||||||||||||||||||||||||
| Re: Rejection number | |||||||||||||||||||||||||
How to Read This Table?
For example, if your lot size is between 3,201 and 10,000 pieces and your inspection level is 'II', the code letter would be 'L'. This means you need to randomly select 200 pieces from the lot size. If your AQL is set at 2.5% for major defects and 4.0% for minor defects, the products are acceptable if no more than 10 major defects and no more than 14 minor defects are found. For instance, finding 15 major defects and 12 minor defects would result in rejection, while finding 3 major defects and 7 minor defects would be acceptable.