AQL (Acceptable Quality Limit) tables tell inspectors how many pieces to check and how many defects are allowed. The tables below follow ANSI/ASQ Z1.4-2008 (US) and ISO 2859-1 (EU) for normal inspection.
Table I: Sample size by lot size
Find your lot size, then read across for your inspection level. General level II is the default. Special levels S1 to S4 are used for measurements and tests.
| Lot size | S1 | S2 | S3 | S4 | I | II | III |
|---|---|---|---|---|---|---|---|
| 2 to 8 | 2 | 2 | 2 | 2 | 2 | 2 | 3 |
| 9 to 15 | 2 | 2 | 2 | 2 | 2 | 3 | 5 |
| 16 to 25 | 2 | 2 | 3 | 3 | 3 | 5 | 8 |
| 26 to 50 | 2 | 3 | 3 | 5 | 5 | 8 | 13 |
| 51 to 90 | 3 | 3 | 5 | 5 | 5 | 13 | 20 |
| 91 to 150 | 3 | 3 | 5 | 8 | 8 | 20 | 32 |
| 151 to 280 | 3 | 5 | 8 | 13 | 13 | 32 | 50 |
| 281 to 500 | 3 | 5 | 8 | 13 | 20 | 50 | 80 |
| 501 to 1,200 | 5 | 5 | 13 | 20 | 32 | 80 | 125 |
| 1,201 to 3,200 | 5 | 8 | 13 | 32 | 50 | 125 | 200 |
| 3,201 to 10,000 | 5 | 8 | 20 | 32 | 80 | 200 | 315 |
| 10,001 to 35,000 | 5 | 8 | 20 | 50 | 125 | 315 | 500 |
| 35,001 to 150,000 | 8 | 13 | 32 | 80 | 200 | 500 | 800 |
| 150,001 to 500,000 | 8 | 13 | 32 | 80 | 315 | 800 | 1250 |
| 500,001 and over | 8 | 13 | 50 | 125 | 500 | 1250 | 2000 |
Table II-A: Accept / Reject numbers (normal inspection)
Read down to your sample size and across to your AQL. Each cell shows Ac/Re: accept the lot if defects found are at or below Ac, reject if at or above Re. ↓ means use the first Ac/Re below it (a larger sample size). ↑ means use the Ac/Re above it (a smaller sample size, 21/22 at most).
| AQL | 2 | 3 | 5 | 8 | 13 | 20 | 32 | 50 | 80 | 125 | 200 | 315 | 500 | 800 | 1250 | 2000 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 0.065 | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 |
| 0.10 | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 | 5/6 |
| 0.15 | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 | 5/6 | 7/8 |
| 0.25 | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 | 5/6 | 7/8 | 10/11 |
| 0.40 | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 | 5/6 | 7/8 | 10/11 | 14/15 |
| 0.65 | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 | 5/6 | 7/8 | 10/11 | 14/15 | 21/22 |
| 1.0 | ↓ | ↓ | ↓ | ↓ | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 | 5/6 | 7/8 | 10/11 | 14/15 | 21/22 | ↑ |
| 1.5 | ↓ | ↓ | ↓ | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 | 5/6 | 7/8 | 10/11 | 14/15 | 21/22 | ↑ | ↑ |
| 2.5 | ↓ | ↓ | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 | 5/6 | 7/8 | 10/11 | 14/15 | 21/22 | ↑ | ↑ | ↑ |
| 4.0 | ↓ | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 | 5/6 | 7/8 | 10/11 | 14/15 | 21/22 | ↑ | ↑ | ↑ | ↑ |
| 6.5 | ↓ | ↓ | 0/1 | 1/2 | 2/3 | 3/4 | 5/6 | 7/8 | 10/11 | 14/15 | 21/22 | ↑ | ↑ | ↑ | ↑ | ↑ |
Quick reference
- General level I: smaller sample, for low risk and a good supplier history.
- General level II: standard, used in most inspections.
- General level III: larger sample, for high risk or past quality problems.
- Common AQL: Critical 0, Major 2.5, Minor 4.0.
Worked example
Lot size 20,000, general level II, Major AQL 2.5 and Minor AQL 4.0. The sample size is 315 pieces. Major: accept up to 14 defects, reject at 15. Minor: accept up to 21 defects, reject at 22.
Want it calculated for you? Use the AQL Calculator.