A lot size plus an inspection level gives a sample size code letter; the code letter gives the sample size; the sample size and the AQL give the accept and reject numbers. This table runs that chain for General Inspection Levels I, II and III under ISO 2859-1, with AQL 2.5 at General Inspection Level II as the programme standard.
Sample size is set by the lot size and the inspection level, not by preference. Enter the lot size, and the chain runs in one direction: lot band to sample size code letter, code letter to sample size, and sample size plus AQL to the accept and reject numbers. At AQL 2.5 under ISO 2859-1, General Inspection Level II, a lot in the thousands of pieces returns a code letter and a sample size in the low hundreds.
What Is an AQL Sampling Table Actually For?
An AQL sampling table converts a lot size into a decision rule that both sides can check before production starts. The acceptable quality limit is the worst tolerable process average when a continuing series of lots is submitted, and the table turns that idea into three numbers: how many pieces get pulled, how many defects still pass the lot, and how many defects fail it. Without those three numbers an inspection is an opinion, and opinions are renegotiated on the day.
AQL sampling table
Table lookupResult
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| Plan | AQL 2.5 | AQL 2.5 |
|---|
Enter the lot size offered for inspection. The plan is normal inspection, single sampling, per ISO 2859-1. Where the standard sets a plan by an arrow rather than printing a pair, the table asks you to confirm instead of printing a guess.
Indicative only, and a plan rather than a promise. The sample size and the accept and reject numbers belong in the purchase order before production starts, and every pair should be confirmed against the current ISO 2859-1 table.
The panel prints the programme standard in the middle column and the level the buyer selected in the right-hand one, so the effect of moving off AQL 2.5 is visible as a number rather than as a feeling. What it will not do is pretend that a tighter level costs nothing: a lower accept number at the same sample size rejects more lots, and a rejected lot costs a schedule, not a score.
How Does a Lot Size Become a Sample Size Code Letter?
The chain has three links and no shortcuts. The lot size falls into a band; that band carries a sample size code letter; the code letter fixes the sample size. Only then does the AQL column come into play, returning the accept and reject numbers for that sample size. The bands are not linear, which is the part buyers find counter-intuitive: doubling the lot does not double the sample.
| Lot size (pcs) | Code letter | Sample size (pcs) | Ac / Re at AQL 2.5 |
|---|---|---|---|
| 2 to 8 | A | 2 | 0 / 1 |
| 9 to 15 | B | 3 | 0 / 1 |
| 16 to 25 | C | 5 | 0 / 1 |
| 26 to 50 | D | 8 | 0 / 1 |
| 51 to 90 | E | 13 | 1 / 2 |
| 91 to 150 | F | 20 | 1 / 2 |
| 151 to 280 | G | 32 | 2 / 3 |
| 281 to 500 | H | 50 | 3 / 4 |
| 501 to 1200 | J | 80 | 5 / 6 |
| 1201 to 3200 | K | 125 | 7 / 8 |
| 3201 to 10000 | L | 200 | 10 / 11 |
| 10001 to 35000 | M | 315 | 14 / 15 |
| 35001 to 150000 | N | 500 | 21 / 22 |
| 150001 to 500000 | P | 800 | 21 / 22 |
| 500001 and over | Q | 1250 | 21 / 22 |
The reason the sample grows so slowly is statistical rather than commercial. A sample of 125 drawn from a lot of 3,200 and a sample of 200 drawn from a lot of 10,000 give broadly comparable discrimination, because what matters is the absolute number of pieces examined rather than the share of the lot they represent. A buyer who insists on a percentage sample is paying for pieces that change the answer very little.
What Do the Accept and Reject Numbers Oblige You to Do?
The accept number is the largest number of defects that still passes the lot; the reject number is the smallest number that fails it. The obligation sits on the buyer: a lot that reaches the reject number has failed, and the buyer must then decide what to do with the whole lot rather than with the pieces examined. Doing nothing after a failure is the one option the standard does not contemplate.
- Accept the lot as it stands, with the defect rate recorded against the lot in the inspection report.
- Require a full rework or sort of the lot at the production site, then present the lot for a second inspection.
- Accept the lot with a written deviation covering the specific defect, agreed before the goods ship.
- Reject the lot and require a remake, which restarts the clock on the bulk window rather than pausing it.
- Record the failure, because a series of failures is what moves inspection from normal to tightened.
Why Is General Inspection Level II the Default Here?
General Inspection Level II is the level most consumer-goods programmes write into the purchase order, and it is the level this programme quotes. Level I pulls a smaller sample and is used when inspection cost is high relative to the cost of the defect; Level III pulls a larger sample when discrimination matters more than the inspection fee. Special levels S-1 to S-4 exist for destructive or expensive tests and are not used for general appearance inspection.
| Inspection level | Code letter against Level II | When it is used | Effect on the sample |
|---|---|---|---|
| General Level I | One code letter smaller | When inspection cost is high against the cost of the defect | A materially smaller sample and a weaker plan |
| General Level II | As tabulated | The default for this programme | The sample published in the purchase order |
| General Level III | One code letter larger | When a defect is expensive downstream and discrimination matters more | A materially larger sample at a higher inspection cost |
| Special levels S-1 to S-4 | Set separately in the standard | Destructive or costly tests on a small number of pieces | Small samples, not used for general appearance inspection |
Why Is AQL 1.5 Not a Standard Preferred Level?
AQL 1.5 is quoted by some suppliers as a mark of strictness, and it does sit as a column in the standard's tables. It is not, however, one of the levels normally written into a general consumer-goods inspection plan, where the series in common use runs 0.65, 1.0, 2.5, 4.0 and 6.5. Publishing a level outside that series makes the plan harder to reproduce, harder to check against the standard and easier to argue about on inspection day.
What changes when the level moves off 2.5
- A smaller AQL lowers the accept number at the same sample size, so more lots fail on the same defect count.
- A plan that is harder to reproduce is a plan that gets renegotiated when a lot is already late.
- A tighter level does not tighten the process; it only moves where the accept and reject line is drawn.
- Where a level outside the common series is wanted, the pairs must be confirmed against the current ISO 2859-1 table.
- This programme publishes AQL 2.5 at General Inspection Level II and writes both into the purchase order.
What Do the Switching Rules Do Over a Series of Lots?
Sampling is not a single event; it is a series, and ISO 2859-1 moves the plan between normal, tightened and reduced inspection according to how that series performs. The switching rules are what turn a one-off inspection into a system: a supplier whose lots keep passing earns a smaller sample, and one whose lots keep failing earns a lower accept number at the same sample size.
| State | How it is entered | What changes |
|---|---|---|
| Normal | At the start of inspection on a new programme | The published plan: sample size, accept and reject numbers as tabulated |
| Tightened | When a defined number of lots in a short series is rejected on original inspection | The same sample size with a lower accept number |
| Reduced | After a sustained run of accepted lots with production at a steady rate | A smaller sample, with the plan set by the standard for that state |
| Discontinued | When tightened inspection remains in place without improvement | Provision under the plan stops until the cause is addressed |
The practical consequence for a buyer is that the first inspection is only the beginning of the record. A programme that fails two lots out of five consecutive ones moves to tightened inspection, and the accept number drops while the sample size does not — which is precisely the pressure the rules are designed to apply. Conversely, a steady run of accepted lots is what earns a reduced sample and lower inspection cost later.
What Happens When the Lot Is Too Small for the Code Letter?
Sometimes the sample size the code letter gives is not smaller than the lot itself, and in that case there is nothing to sample. A lot of 20 pieces against General Inspection Level III returns a code letter whose sample is a large share of the lot, and a lot of five returns a sample equal to it. The rule is plain: where the sample is not smaller than the lot, inspection is 100%, and a reduced plan or a defined first-article check is the sensible route.
- Below the minimum lot for a code letter, examine every piece and record the defects against the full lot.
- For pre-production and sales samples, a first-article check against the tech pack serves better than a sampling plan.
- MOQ 500 pcs per style and colourway means most production lots sit well inside a tabulated band.
- Small lots that repeat are better handled as a series under the switching rules than as isolated events.
- The tool states plainly when the sample equals or exceeds the lot rather than printing a plan that cannot be drawn.
- Programme inspection standard
- AQL 2.5, ISO 2859-1, General Inspection Level II
- Plan type
- Normal inspection, single sampling, switching rules applied by default
- Defect classes
- Critical, major and minor, each with its own AQL and its own accept and reject numbers
- Where the plan is written
- The purchase order, before production starts, and repeated in the inspection report
- MOQ
- 500 pcs per style and colourway (300 on a repeat)
- Sampling and bulk timing
- Sampling 6-10 working days, bulk 35-50 days from sample approval
- Commercial terms
- FOB Xiamen, T/T 30/70
How Does the Sample Size Get Written Into the Purchase Order?
As a clause with four fields in it: the standard, the inspection level, the AQL for each defect class, and the consequence of reaching the reject number. Naming the standard and the level is enough to derive the sample size, but writing the sample size itself removes any room to argue on the day. A clause that says only AQL 2.5 leaves three of those four fields open, and every open field is a field that gets negotiated after the goods are packed.
The defect classes matter as much as the level. Critical defects — a broken needle left in a seam, a sharp edge on hardware — carry an accept number of zero in most published plans and are never sampled into tolerance. Major and minor defects carry their own AQL, and the defect dictionary for major and minor is what stops that classification becoming a discussion at the folding table.
Where Does the Table Stop and a Defect List Start?
At the point where the question stops being how many and becomes what. The table can say that 125 pieces get pulled from a lot of 3,200 and that the eighth defect fails it; it cannot say whether a crooked seam is a major or a minor, because that depends on the construction and on the end use. Those definitions belong to a defect list agreed in writing, and they are specific to the category: a camera bag divider that lifts is a failure, while the same stitch on a drawstring bag may be cosmetic.
So the sequence is: fix the plan with this table, fix the definitions with the defect list, then fix the consequence in the purchase order. A buyer who has done all three before production starts does not negotiate on inspection day; a buyer who has done two of them does. The landed cost calculator sits on the other side of the same decision, because a rejected lot costs freight days that no unit price recovers.
Fix the plan before the cartons are packed
Run the table on your lot size, write the code letter, the sample size and the accept and reject numbers into the purchase order, and send the specification with them attached. The programme runs on AQL 2.5 at General Inspection Level II, MOQ 500 pcs per style, sampling in 6-10 working days and bulk in 35-50 days, FOB Xiamen.
Frequently Asked Questions
What does AQL stand for and what does it actually mean?
AQL is the acceptable quality limit: the worst tolerable process average when a continuing series of lots is submitted for acceptance sampling. It is not a promise that a lot contains no more than 2.5% defects. It is the quality level the sampling plan is built around, and ISO 2859-1 turns it into a sample size and a pair of numbers.
Why is AQL 2.5 used here rather than 1.5?
AQL 2.5 sits inside the series of levels normally written into general consumer-goods inspection plans, alongside 0.65, 1.0, 4.0 and 6.5. A level of 1.5 appears as a column in the standard's tables but is not one of the levels commonly used, which makes the plan harder to reproduce and easier to argue about during inspection.
What is General Inspection Level II?
It is the default general inspection level in ISO 2859-1 and ANSI Z1.4, and it sets which sample size code letter a lot band carries. Level I takes the code letter one step smaller and Level III one step larger, so the same lot returns three different sample sizes depending on the level chosen in advance.
How is the sample size worked out from a lot size?
The lot size falls into a band, the band carries a sample size code letter, and the code letter fixes the sample size. The AQL column then gives the accept and reject numbers for that sample size. The bands are not proportional: a larger lot pulls a larger sample, but not a proportionally larger one.
What is the difference between the accept and the reject number?
The accept number is the largest count of defects that still passes the lot; the reject number is the smallest count that fails it. There is no gap between them in a single sampling plan. Once the reject number is reached the lot has failed, and the buyer must decide what happens to the whole lot.
What does a rejected lot oblige the buyer to do?
To act on the whole lot rather than on the pieces examined: accept it with the defect rate recorded, require a rework and a second inspection, agree a written deviation, or reject it and require a remake. Doing nothing after a failure is not an option the plan contemplates, and a failure also counts towards the switching rules.
What happens when the lot is smaller than the sample size?
There is nothing to sample. Where the sample size the code letter gives is not smaller than the lot, inspection becomes 100% of the pieces present, or a reduced plan or a first-article check is used instead. The tool states this plainly rather than printing a plan that cannot be drawn.
Do the switching rules apply to a single order?
They apply across a series of lots, which is how ISO 2859-1 is designed to be used. Lots that keep failing move inspection to tightened, with the same sample size and a lower accept number; a sustained run of accepted lots with steady production can move it to reduced, with a smaller sample.
Can the accept and reject numbers be changed after production starts?
They can be agreed, but changing them after the goods are packed is a renegotiation of the plan rather than an inspection. The numbers belong in the purchase order before production starts, together with the standard, the inspection level and the defect classes, so that nothing is open on the day.
Does a tighter AQL give a better bag?
No. It gives a stricter pass or fail line on the same process. A lower accept number at the same sample size rejects more lots, which costs schedule and rework time rather than improving the construction. Process control and a defect list agreed in writing are what change the bag itself.
Which standard should be named in the purchase order?
ISO 2859-1 for sampling procedures for inspection by attributes, or ANSI/ASQ Z1.4 where the buyer works to the American series. Name the standard, the inspection level, the AQL for each defect class and the consequence of a failure; writing the sample size as well removes the last field open to argument.
People Also Ask
What is a fair sample size for inspecting a bag order?
The one the standard gives for the lot band and the inspection level, not one chosen by preference. At General Inspection Level II under ISO 2859-1 a lot in the low thousands returns a code letter whose sample is in the low hundreds, and that sample is the same for every supplier on the same lot.
What does AQL 2.5 mean on a 500-piece order?
A lot of 500 pieces sits in the band that carries code letter H, giving a sample size of 50 pieces with an accept number of 3 and a reject number of 4 at AQL 2.5. Four defects in that sample fail the lot, and the buyer then decides whether to accept, rework, deviate or reject the whole 500.
Why is AQL 1.5 not used as a standard level?
It appears as a column in the standard's tables but is not one of the levels normally written into general consumer-goods plans, where the common series runs 0.65, 1.0, 2.5, 4.0 and 6.5. Quoting it as a mark of strictness produces a plan that is harder to reproduce and easier to dispute on inspection day.
What happens if a bag order fails inspection?
The lot has failed, not the sample. The buyer accepts it with the defect rate recorded, requires a rework and a second inspection, agrees a written deviation, or rejects it and requires a remake — and the failure counts towards the switching rules that move inspection to tightened.
Do critical defects follow the same AQL as minor ones?
No. Critical, major and minor defect classes carry their own AQL and their own accept and reject numbers, and critical defects carry an accept number of zero in most published plans. The classification itself has to be agreed in a written defect list before production, not decided at the folding table.
Sources and further reading
Every figure on this page is either our own programme data or attributed below. Open the originals before you write them into a specification.
- ISO 2859-1 sampling procedures for inspection by attributesInternational Organization for Standardization
- Acceptance sampling standards and ANSI/ASQ Z1.4American Society for Quality
- Incoterms 2020 rulesInternational Chamber of Commerce