AQL Calculator
How many pieces to check, and how many defects before the lot fails? Get the answer in seconds from the ISO 2859-1 sampling tables.
For a lot of 5,000 pieces at general inspection level II, the inspector checks 200 pieces: the lot is rejected at 1 critical defect, 11 major defects (AQL 2.5) or 15 minor defects (AQL 4.0). Enter your own quantity and AQL values to get your limits.
Simulation based on ISO 2859-1 (MIL-STD-105E) single sampling plans, normal inspection. Indicative only. “Not allowed” means zero defects tolerated: the sample size is kept and the lot is rejected on the first defect found.
How to use the AQL calculator
- Lot size: the quantity presented for inspection, usually the quantity ordered.
- Inspection level: level II is the default. Level I checks fewer pieces (a supplier with a good track record), level III more (after a failed inspection).
- AQL per defect type: the usual settings for consumer goods are 0 for critical defects, 2.5 for major and 4.0 for minor.
- Reading the result: “Sample” is the number of pieces to check; “Accept”, the maximum number of defects for the lot to pass; “Reject”, the number of defects at which the lot fails.
Quick reference at level II (AQL 2.5 and 4.0)
The most common cases, taken from Tables A and B of ISO 2859-1 (normal inspection, single sampling), identical to ANSI/ASQ Z1.4. Each cell reads: accept up to / reject at.
| Lot size | Code letter | Sample | Major (AQL 2.5) | Minor (AQL 4.0) |
|---|---|---|---|---|
| 281 to 500 | H | 50 | 3 / 4 | 5 / 6 |
| 501 to 1,200 | J | 80 | 5 / 6 | 7 / 8 |
| 1,201 to 3,200 | K | 125 | 7 / 8 | 10 / 11 |
| 3,201 to 10,000 | L | 200 | 10 / 11 | 14 / 15 |
| 10,001 to 35,000 | M | 315 | 14 / 15 | 21 / 22 |
To understand where these figures come from, choose an inspection level or read the full table, see our AQL guide. To see where AQL sampling fits in the whole process, read our guide to quality control in China.
Frequently asked questions
Why does the sample size differ between defect types?
Because Table B of ISO 2859-1 does not hold a usable plan for every combination: when an AQL is too low or too high for the code letter, an arrow sends you to the nearest row that has one. For 5,000 pieces at level II, an AQL of 0.065 therefore needs 315 pieces instead of 200, with rejection on the first defect. The calculator follows these arrows.
What if the lot is smaller than the sample size?
Every piece is checked (100% inspection) and the lot is rejected on the first defect. This happens, for example, with a lot of 40 pieces at an AQL of 0.40: the table would ask for 50 pieces. The calculator then shows the lot size as the sample.
Is the calculator result binding on the factory?
No, it is indicative. What binds the supplier are the AQL values and the inspection level written in the purchase order or contract before production starts. On the day of the pre-shipment inspection, the inspector applies those values to the standard’s tables.
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