AQL chart for garment inspection: 2.5 and 4.0 explained

An AQL chart turns two facts, the size of your lot and the AQL you agreed, into three numbers: how many garments to inspect, how many defects you can accept, and the count at which the lot fails. For most apparel at General Inspection Level II, a lot of 3,201 to 10,000 pieces means inspecting 200 garments; at AQL 2.5 the lot passes with 10 major defects or fewer and fails at 11. At AQL 4.0 the same 200 pieces may carry 14 minor defects and fail at 15.

What does AQL 2.5 actually mean?

AQL stands for Acceptance Quality Limit. It is the index that selects a sampling plan from the tables in ISO 2859-1, which uses the same tables as the American ANSI/ASQ Z1.4. The US National Institute of Standards and Technology describes the AQL as the baseline quality requirement for the producer’s product: a percent defective the process should be able to stay under.

So “AQL 2.5” is not a promise that 2.5% of your garments will be faulty, and it is not a guarantee that only 2.5% are. It is a rule for a decision. You draw a random sample of a fixed size, count what you find, and compare the count with an accept number and a reject number. Apparel orders usually carry two limits at once: 2.5 for major defects and 4.0 for minor defects, with critical defects set at zero. The quality control page explains how we apply those limits on an order. This article is about reading the chart itself.

Step 1: how do you find the sample size code letter?

The first table converts lot size into a code letter. The lot is the quantity presented for inspection, normally the whole order for one style from one factory. Pick the row for your lot size, then the column for your inspection level. Level II is the default unless the buyer specifies otherwise.

Read from the ISO 2859-1 code letter table as reproduced by Asia Quality Focus and Tetra Inspection, checked 22 September 2026. The letter is not a sample size yet. It is a pointer into the second table.

Step 2: how do you read the sample size and accept and reject numbers?

The second table, single sampling plans for normal inspection, gives each letter a sample size and, under each AQL column, an Ac (accept) and Re (reject) number. If the defects found are equal to or below Ac, the lot is accepted. If they reach Re, it is rejected. In the normal single sampling table there is no grey zone: Re is always Ac plus one.

Figures read from the ISO 2859-1 (ANSI/ASQ Z1.4) normal inspection table published by Asia Quality Focus, with the L row cross-checked against QIMA and the L and M rows against Tetra Inspection, 22 September 2026. We have reproduced the table, not calculated it. Always confirm against the table your inspector or your retailer’s manual uses.

A worked example: 2,400 hoodies at AQL 2.5 and 4.0

Say one style of hoodie, 2,400 pieces, made in one factory, is ready for final inspection at General Level II with AQL 2.5 major and 4.0 minor.

• Code letter: 2,400 falls in 1,201 to 3,200, so Level II gives K.
• Sample: K means 125 pieces, drawn at random across colours, sizes and cartons.
• Majors at AQL 2.5: accept with 7 or fewer, reject at 8.
• Minors at AQL 4.0: accept with 10 or fewer, reject at 11.
• Criticals: one is enough to reject.

The two counts are judged separately. Six majors and eleven minors fail the lot on minors, even though the majors passed. Six majors and ten minors pass both. A lot can fail on a single critical defect, such as a broken needle point, whatever the other two counts say.

Notice what the chart does not do. It does not scale neatly with quantity. A lot of 1,201 pieces and a lot of 3,200 pieces both get a sample of 125. That is deliberate: the tables protect the buyer more on larger lots, where the sample is a smaller share but the evidence is stronger.

What do the arrows mean, and what about small lots?

Some cells in the printed table hold an arrow instead of numbers. That happens where the sample for that letter is too small to support the chosen AQL. The instruction printed with the table is to use the first sampling plan the arrow points to, and to use that plan’s sample size as well as its numbers. If the sample size then equals or exceeds the lot, inspect every piece.

This is why small orders feel expensive to inspect. A lot of 120 pieces at Level II needs 20 garments checked, a sixth of the order. For runs made through a small-run route, a buyer can accept that proportion, or check every piece of a first order and move to sampling once the factory has earned it.

Level I, II or III: which inspection level should you use?

ISO 2859-1 offers three general levels. Level II is the default. Level I inspects fewer pieces and discriminates less; Level III inspects more and discriminates more. On a lot of 3,201 to 10,000 pieces, the choice changes the sample from 80 (Level I, letter J) to 200 (Level II, letter L) to 315 (Level III, letter M).

The table also has four special levels, S-1 to S-4, with much smaller samples. The Asia Quality Focus chart notes that these are only used for special checks or testing. In apparel they suit checks that cost a garment or a lot of time per piece, such as a full measurement check against every point on the spec or a destructive seam test, where a small sample is agreed in advance.

A careful buyer changes the level for a reason and writes it into the order: Level III on a first order with a new factory, or a tighter AQL of 1.5 on majors for a premium product, as Tetra Inspection notes some brands do.

Tightened, reduced and skip-lot inspection

AQL tables were designed for a continuing series of lots from one producer, not a single shipment. The introduction to ISO 2859-1 says the scheme protects the buyer by switching to tightened inspection when quality deteriorates, and rewards consistent quality by switching to a smaller sample. Tetra Inspection summarises the usual trigger: tightened inspection starts when two of five consecutive lots fail.

• Normal: where every relationship starts, and the table above.
• Tightened: stricter acceptance criteria, used after repeated failures until quality recovers.
• Reduced: smaller samples after a run of accepted lots and steady production, at the discretion of the buyer or its quality team.
• Skip-lot: inspecting only randomly chosen lots once a producer is qualified. This is new in the 2026 edition.

For a brand placing two or three orders a year, the switching rules rarely come into play. They matter once you run repeat programmes with the same factory, and they are a good reason to keep inspection records in one place.

Did ISO 2859-1:2026 change the AQL chart?

ISO published a third edition, ISO 2859-1:2026, which cancels and replaces the 1999 edition. Its foreword lists the main changes: a new procedure for switching to skip-lot inspection, guidance on qualifying producers and products for it, guidance on randomly selecting lots, and the removal of the printed operating characteristic curves in favour of methods to construct them. The code letters and the acceptance tables are not in that list of changes.

So a chart printed from the 1999 edition still gives the same answers for normal single sampling. What changes is the paperwork: new contracts and quality manuals should cite the 2026 edition, and anyone offering skip-lot inspection should be able to show how they qualified the factory for it.

Five mistakes people make reading the chart

• Treating two factories as one lot. The standard applies to lots from one producer using one process; different producers are sampled separately.
• Counting defects when you meant defective pieces. The standard supports both nonconforming items and nonconformities per 100 items. Agree which one the report will count: a shirt with three faults is one defective piece but three defects.
• Sampling from the top cartons. The sample must be random across the lot, or the statistics mean nothing.
• Inspecting before the goods exist. QIMA runs pre-shipment inspection when at least 80% of the order is complete, so the sample represents the lot.
• Agreeing an AQL without defining a major. The chart counts; it does not classify. Classification lives in your tech pack and defect list.

What to do next

Put the inspection standard, level and AQLs in the purchase order before production, next to the sealed sample and the measurement tolerances in your tech pack. If you are producing hoodies, t-shirts or anything else in Bangladesh and want the inspection plan agreed before a single piece is cut, see how we work or send us your quantities and style list and we will set out the sample sizes that apply.