How to Read AQL Tables
AQL inspection uses two tables from the ISO 2859-1 standard:
Table 1: Sample Size Code Letters
- Find your lot (order) size in the rows
- Choose inspection level (usually Level II)
- Get the "code letter" (A through R)
Table 2: Accept/Reject Limits
- Find your code letter in the rows
- Find your AQL level in the columns
- Get sample size and Ac (accept) / Re (reject) numbers
Finding Your Sample Size
| Lot Size | Level I | Level II | Level III |
|---|---|---|---|
| 2-8 | A | A | B |
| 9-15 | A | B | C |
| 16-25 | B | C | D |
| 26-50 | C | D | E |
| 51-90 | C | E | F |
| 91-150 | D | F | G |
| 151-280 | E | G | H |
| 281-500 | F | H | J |
| 501-1200 | G | J | K |
| 1201-3200 | H | K | L |
| 3201-10000 | J | L | M |
| 10001-35000 | K | M | N |
Accept/Reject Numbers (AQL 2.5)
| Code | Sample Size | Accept (Ac) | Reject (Re) |
|---|---|---|---|
| D | 8 | 0 | 1 |
| E | 13 | 1 | 2 |
| F | 20 | 1 | 2 |
| G | 32 | 2 | 3 |
| H | 50 | 3 | 4 |
| J | 80 | 5 | 6 |
| K | 125 | 7 | 8 |
| L | 200 | 10 | 11 |
| M | 315 | 14 | 15 |
Practical Example
Scenario: You ordered 3,000 units. How many to inspect?
- Find lot size range: 1201-3200 → Code Letter K (Level II)
- Look up sample size: Code K = 125 samples
- For AQL 2.5: Accept if ≤7 defects, Reject if ≥8 defects
How to apply:
- Pull 125 random samples from the shipment
- Inspect each for defined defects
- Count major defects found
- If 7 or fewer → PASS
- If 8 or more → FAIL
Tip: Use separate AQL values for critical (0), major (2.5), and minor (4.0) defects. A batch might pass for minor defects but fail for major ones.