AQL sample size calculator, from the national standard

Enter your lot size, inspection level and AQL. The calculator returns the sample size and the accept and reject numbers for single sampling under normal inspection, from GB/T 2828.1-2012, the Chinese national standard identical to ISO 2859-1:1999.

Reading your result

Start with the code letter. Table 1 of the standard turns your lot size and inspection level into a sample size code letter (样本量字码), from A to R. The letter picks a row in Table 2-A, and that row gives the sample size, from 2 units for A to 2,000 for R. If the report you get back is in Chinese, the terms in brackets on this page are the ones to look for.

The inspector then draws the sample and checks each unit, keeping a tally of the nonconforming ones. If the tally is at the acceptance number (接收数, Ac) or below, the lot passes; at the rejection number (拒收数, Re) or above, it fails. In every plan in Table 2-A, Re is one more than Ac, so there is no count in between.

Sometimes the plan comes from another row. Some cells of Table 2-A hold an arrow instead of a plan, and the note under the table says what to do with each kind:

Follow an arrow and the sample size changes with it. Say you have 500 units at level II. That’s code letter H, a sample of 50. At an AQL of 0.65, the H cell points down, so the plan is J’s: 80 units, accept on 1, reject on 2.

The note ties the 100% rule to the downward arrow. The calculator applies it to every plan, because no sample can be bigger than the lot it comes from. A lot of 4 units at level II and AQL 2.5 lands on a plan of 5 units, so you check all 4.

Choosing the inspection level

Table 1 has seven levels. Three are general inspection levels (一般检验水平): I, II and III. Four are special inspection levels (特殊检验水平): S-1 to S-4. Moving up the levels never shrinks the sample. Here is what each one means for a lot of 1,000 units:

Open more units and a lot with problems is more likely to show them. It also takes longer. The level belongs in the order, next to the AQL. If your order doesn’t name one, settle it with the supplier before the inspection, not after the count.

Choosing an AQL

The acceptance quality limit (接收质量限), or AQL, is agreed between buyer and supplier in the contract or the purchase order. China’s national statistics vocabulary defines it in one line:

Two numbers get mixed up here. The AQL is the column you read; Ac is the count of bad units the plan lets through, and for a given AQL it grows with the sample. This page doesn’t recommend an AQL, and no value is an industry rule. An order can set more than one, for example one for each class of defect. Enter them all; the calculator takes up to three.

Which plan this is

The calculator gives one kind of plan, and only one: single sampling under normal inspection (正常检验), the plans of Table 2-A. When the order or the inspector’s report names a different table, these numbers are not the ones to use. Ask which table applies before the inspection starts.

What AQL sampling does not tell you

If you came for the numbers, you have them by now. This part is about what they can’t do.

An AQL of 2.5 is not a promise that 2.5% of the lot, or less, is defective. Take a lot of 1,000 units at level II and AQL 2.5:

Sampling can’t find every defect. In that lot, 920 units are never opened. A lot that passes on its sample can still hold nonconforming units, so decide in advance what happens if they turn up after delivery, and write it into the order.

A count against a plan is also a different job from a factory visit. A one-day visit by someone on the ground tells you whether the factory is what you were told it is. It doesn’t pull a sample from a finished lot. For what a count costs, see what drives the cost of a factory inspection in China.

Where these tables come from

The standard is GB/T 2828.1-2012, 计数抽样检验程序 第1部分：按接收质量限(AQL)检索的逐批检验抽样计划 (Sampling procedures for inspection by attributes, Part 1: Sampling schemes indexed by acceptance quality limit for lot-by-lot inspection). It was issued on November 5, 2012, and replaced the 2003 edition when it took effect on February 15, 2013. China’s national standards platform lists it as in force. It was last reviewed on May 30, 2025, and the review found it still valid. The same platform states that it adopts ISO 2859-1:1999 identically.

The national standards portal doesn’t display the text of this standard, because it adopts an ISO standard. So the calculator’s tables were transcribed from the copy of Table 1 and Table 2-A printed in DA/T 38-2021, an archives industry standard issued by China’s National Archives Administration, which reproduces both tables and the note on the arrows in a normative appendix. They were then checked cell by cell against a second copy, in DA/T 83-2019. The two agree everywhere but one cell: DA/T 83-2019 prints H for lots of 3,201 to 10,000 at level I, where DA/T 38-2021 prints J. The calculator uses J.

The calculator encodes the numbers of Table 1 and Table 2-A. This page quotes one note and one definition, and doesn’t reproduce the standard’s text. The standard’s entry was read on openstd.samr.gov.cn on October 18, 2026.

Who does the count

It doesn’t matter who does the count. The table is the same for an inspection firm and for a freelancer you hire, as in the guide to hiring a freelance sourcing agent in China. Freelancers who check goods bid in the sourcing and quality control category, and the handbook on hiring a freelancer in China covers contracts and pay.

Put the lot size, the level and the AQL in your brief, and the inspector works from the same plan you looked up here. Start a brief.