AQL sampling plan calculator
Enter a lot size and an AQL, and get the sample size, accept number and reject number for a single sampling plan under normal inspection - the plan a third-party inspector will actually use at your pre-shipment inspection.
Total pieces offered for inspection in this shipment.
Level II unless the buyer's AQL clause says otherwise.
2.5 / 4.0 is the most common garment combination. Critical defects are inspected at Ac 0 - one is enough to fail the lot.
Sample size
125pcs
Code letter K
Lot
1,500pcs
General level II
| Defect class | Sample | Accept | Reject |
|---|---|---|---|
| Critical | 125 | 0 | 1 |
| Major (AQL 2.5) | 125 | 7 | 8 |
| Minor (AQL 4.0) | 125 | 10 | 11 |
Optional - enter what the inspection found
How this is calculated
Acceptance sampling answers one question: how many pieces do I pull from this lot, and how many defects may I find before I stop shipping it? The answer comes from two tables in the standard.
Step 1 - the code letter. The lot size and the inspection level select a sample size code letter from Table I. A lot of 1,500 pieces at general level II gives code letter K. Watch the row boundaries: the row is 1,201–3,200, so a lot of exactly 1,200 falls in the row below and gives J with a sample of 80, not 125.
Step 2 - the plan. The code letter and the AQL select a sample size and an accept number from Table II-A. Code letter K at AQL 2.5 gives a sample of 125 with Ac 7 / Re 8: inspect 125 pieces, accept the lot at 7 or fewer major defects, reject it at 8.
Step 3 - the arrows. Where the table shows an arrow instead of a number, there is no valid plan at that intersection and you must move to the first plan below the arrow. Both the sample size and the accept number change. This is the step most often misread when working from a printed table, so the calculator applies it and says so.
A garment inspection normally runs three defect classes at once against the same sample - critical at Ac 0, majors at one AQL and minors at a looser one. The lot fails if any class reaches its reject number.
Questions
- What does AQL 2.5 actually mean?
- It is the Acceptable Quality Limit: the defect rate that, over a long run of lots, the sampling plan is designed to accept about 95% of the time. It is a property of the plan, not a promise about any one shipment, and it is not a target defect rate to aim for.
- Which inspection level should I use?
- General level II unless the buyer specifies otherwise. Level I gives a smaller sample and is used when inspection is expensive or the supplier has a strong history; level III gives a larger sample and is used when a supplier is on probation or the product is high risk.
- Why is the sample size sometimes bigger than the code letter suggests?
- The standard’s table marks some combinations with a downward arrow, meaning there is no valid plan at that code letter and AQL, so you must drop to the first plan below the arrow - which changes both the sample size and the accept number. This calculator follows the arrow for you and tells you when it did.
- How are critical defects handled?
- Critical defects - anything that makes the product unsafe or unlawful - are conventionally inspected at zero accept on the same sample as the major plan. One critical defect fails the lot. Some buyers run a separate AQL 0.065 column instead; check the AQL clause in your contract.
- What if the sample size is larger than the lot?
- Inspect 100% of the lot. The standard states this directly, and the calculator flags it when it happens.
- Does this cover tightened and reduced inspection?
- No. This calculator covers single sampling under normal inspection only. Switching to tightened or reduced inspection depends on the supplier’s recent inspection history, which a calculator cannot know, so applying those rules automatically would be misleading.
Sources & verification
The tables used here are the sample size code letters (Table I) and the single sampling plans for normal inspection (Table II-A) from ISO 2859-1, published in the United States as ANSI/ASQ Z1.4. The two are equivalent for the plans shown.
Scope is limited on purpose: single sampling, normal inspection, general inspection levels I–III, and AQLs 1.0 through 6.5. Double and multiple sampling, special inspection levels S-1 to S-4, and the switching rules for tightened and reduced inspection are not implemented.
Check the result against your buyer's own AQL clause before acting on it. Where a contract and a standard disagree, the contract governs the shipment.