AQL Chart Explained: The Complete Guide to Acceptable Quality Limit Sampling

You received 500 units from your factory and eight arrived broken. Is that a normal margin, or grounds for rejecting the shipment? AQL is the standard that answers that question, before your goods leave the factory floor.

AQL, short for Acceptable Quality Limit, is the maximum number of defective units a sample can contain while still allowing the full batch to pass inspection. It turns a vague argument with your supplier into a clear, numbers-based decision.

In this guide, you'll find the AQL sampling chart, a free calculator, and a real product example, so you can decide the right AQL for your next shipment. No statistics background required.

What Is AQL (Acceptable Quality Limit)?

AQL stands for Acceptable Quality Limit. It comes from statistical quality control and is standardized worldwide in ISO 2859-1; which is identical with the domestic standard GB/T 2828.1-2012; And with an identical US version published as ANSI/ASQ Z1.4, original from the US military standard MIL-STD-105.

Here is what AQL does in plain terms. An inspector checks a sample of your goods rather than every single unit. AQL sets the threshold: if the number of defects found in that sample is equal or below the limit, the batch is accepted; if it goes beyond, the batch is rejected.

One misunderstanding is worth clearing up right away. AQL is not a defect rate you agree to tolerate in production. It is a statistical decision rule applied to a sampling, used to infer the likely quality of the whole batch. You are not signing off on bad units. You are setting the point at which a sample tells you the batch is too risky to accept.

In short: AQL tells you what "good enough" means, before your shipment leaves the factory.

How to Read the AQL Sampling Chart (Step-by-Step)

The AQL chart looks intimidating, but reading it is a six-step lookup:

1. Find your lot size. This is the total number of units in the batch you want inspected.
2. Choose your inspection level. General Level II is the default, because it balances sample size against statistical confidence for most orders.
3. Look up the sample size code letter in the ISO 2859-1 table below, based on your lot size.
4. Find the sample size that matches that code letter. This is how many units the inspector will pull and check.
5. Determine your AQL acceptance standard for each defect category (critical, major, minor).
6. Read the accept (Ac) and reject (Re) numbers for your sample size and AQL.

Here is the lot-size-to-sample-size table for General Level II, the most common setting:

Lot size	Sample size (code letter)
2 to 8	2 (A)
9 to 15	3 (B)
16 to 25	5 (C)
26 to 50	8 (D)
51 to 90	13 (E)
91 to 150	20 (F)
151 to 280	32 (G)
281 to 500	50 (H)
501 to 1,200	80 (J)
1,201 to 3,200	125 (K)
3,201 to 10,000	200 (L)
10,001 to 35,000	315 (M)
35,001 to 150,000	500 (N)

A quick worked example. At an AQL of 2.5 for major defect, the accept number is 2 and the reject number is 3: find 2 or lower defects and the batch passes, find 3 or more and it fails; At an AQL of 4.0 for minor defect, the accept number is 3 and the reject number is 4: find 3 or lower defects and the batch passes, find 4 or more and it fails.

That is the whole mechanic. Lot size in, sample size out, then a simple count against your accept and reject numbers.

Free AQL Calculator: Find Your Sample Size in Seconds

If you would rather skip the table lookup, our AQL calculator does the math for you. You enter your lot size and choose your inspection level and AQL values, and it returns your sample size along with the accept and reject numbers for each defect category.

It is the fastest way to build a sampling plan before you brief your supplier or your inspector, and it removes the risk of reading the wrong row.

Try our free AQL calculator.

Prefer to keep a copy on hand? Download our free AQL chart PDF, and share it with your supplier so you both work from the same numbers.

AQL Levels Explained: General I, II, III and When to Use Each

The inspection level decides how many units get checked relative to your lot size. A higher level means a larger sample and more confidence, at a higher inspection cost. ISO 2859-1 defines three general levels and four special ones.

• General Level I: a reduced sample size. Use it when you trust the supplier, have a track record with them, or the product is low-risk and inexpensive.
• General Level II: the standard default. Most importers use this, because it gives a reliable read on batch quality without an oversized sample.
• General Level III: a tightened, larger sample. Use it when a supplier has recent quality problems, or when the product is high-risk and a bad batch would be costly.
• Special Levels S-1 to S-4: much smaller samples, reserved for tests that are destructive or expensive to run, such as unit drop test or full functionality test with built-in, where checking a full-size sample is impractical.

Use this quick guide to pick a level:

Situation	Recommended level
Trusted supplier, low-risk product	I
Default for new importers	II
Supplier with recent quality issues, or high-risk product	III
Destructive tests (unit drop test or full functionality test with built-in)	S-1 to S-4

If you are unsure, start at General Level II. You can tighten to Level III on your next order if the first inspection turns up problems.

Critical, Major, Minor Defects: How AQL Classifies Them

AQL only works once you decide what counts as a defect, and how serious each one is. The standard splits defects into three categories, and you set a separate AQL for each.

• Critical defect: Defects that could result in hazardous or unsafe conditions for individuals using or maintaining the product as well as defects contravening legal regulations. Recommended AQL: 0. In practice this means zero tolerance: a single critical defect rejects the batch.
• Major defect: Defects that could result in reduced usability of the product and/or obvious appearance defects that would affect its sale. Recommended AQL: 2.5, the common setting for general merchandise.
• Minor defect: Any unit having a defect that is not likely to reduce the usability of the unit for its intended purpose. Minor defects also indicate substandard workmanship and areas that need improvement. Recommended AQL: 4.0, or 6.5 on lower-cost cosmetic goods where a wider tolerance still meets buyer expectations..

The standard AQL values you will see on inspection reports are 0.65, 1.0, 1.5, 2.5, 4.0, and 6.5. Tighter values (0.65, 1.0, 1.5) suit high-risk or high-value goods, and looser values (4.0, 6.5) suit low-cost or purely cosmetic categories.

A short example of each defect type. A toy with a detachable small part that a child could swallow is critical. That same toy with malfunction is major. A faint tool mark on the underside is minor.

One warning that saves importers real money: how you classify defects is a negotiation with your supplier, not a fact handed to you. A defect your customer would return might be one your factory calls cosmetic. Agree the classification list in writing before production, not after, and consider a supplier qualification audit before you place a first order with a new factory.

AQL in Practice: A Real Product Inspection Example

Here is how it all fits together on a real order.

An Amazon FBA seller is importing 1,000 Bluetooth speakers from a Chinese factory. It is the first order with this supplier, and the product carries a lithium battery, so safety matters.

Step 1: sample size. A lot of 1,000 units at General Level II falls in the 501 to 1,200 row, giving code letter J and a sample size of 80. The inspector picks 80 speakers at random from the finished and packed goods.

Step 2: AQL values. For consumer electronics with a battery, a sensible sampling plan is 0 critical, 1.5 major, 4.0 minor. The battery risk is why critical sits at zero.

Step 3: accept and reject numbers at a sample size of 80:

• Critical (zero tolerance): accept 0, reject 1
• •    Major (AQL 1.5): accept 3, reject 4
• Minor (AQL 4.0): accept 7, reject 8

On-site, the inspector checks each of the 80 units against your checklist, logs every defect by category, and photographs it. During a pre-shipment inspection we run this while the order is finished and boxed, so the result reflects what would actually ship.

The report tells the seller exactly how many critical, major, and minor defects turned up, with photos, so the accept or reject call is grounded in evidence rather than opinion.

The decision path. Say the inspection finds 6 major defects. That hits the reject number of 6, so the batch fails: the seller can require rework and a re-inspection before shipping. Now say it finds only 2 major defects. That is at or below the accept number of 5, so the batch passes and can ship. Same product, same plan, two clear outcomes.

AQL Standards We Use at AQF

We apply ISO 2859-1 as the default standard on every inspection, which keeps your results consistent with the international norm and its US equivalent, ANSI/ASQ Z1.4.

We follow the AQL values you set. Our default is 0 critical, 2.5 major, 4.0 minor, and we adjust it per product and per contract when your category calls for something tighter or looser.

Our inspection process is managed to the ISO 17020 standard(Recognized by CNAS), the international requirement for third-party inspection bodies. We act as an independent inspector on your behalf, with no commercial ties to your suppliers, so the report you get reflects what your batch actually looks like.

Our inspectors are trained on the sampling chart and on defect classification, so the counts on your report line up with the standard. We record every defect with photos, sorted by severity, so the accept or reject decision stays with you.

To see how this runs on a live order, look at our pre-shipment inspection service, part of our wider product inspection services in China.

Frequently Asked Questions

What is AQL in quality control?

AQL, or Acceptable Quality Limit, is the maximum number of defective units a sample can contain while the full batch still passes inspection. Defined in ISO 2859-1 / ANSI/ASQ Z1.4/ GB/T 2828.1-2012, it converts a sample count into a clear accept or reject decision, so you can judge batch quality without checking every single unit.

What AQL level should I use for my product?

Most importers use 0 for critical defects, 2.5 for major, and 4.0 for minor, at General Inspection Level II; while electronics are using 0 for critical defects, 1.5 major and 4.0 minor,; high-value goods and luxury textile brand are tighten 0 for critical defects, 1.5 major and 2.5 minor. Low-cost cosmetic categories sometimes stretch minor to 6.5. Match the AQL to your product's risk and your customer's expectations.

How is AQL sample size calculated?

Sample size comes from two inputs: your lot size and your inspection level. You find the row for your lot size in the ISO 2859-1 table, read across to your level (General II by default), and it gives a code letter and the matching sample size. A lot of 1,000 units at Level II gives a sample of 80.

What's the difference between AQL 2.5 and AQL 4.0?

AQL 2.5 is stricter than AQL 4.0, so it accepts fewer defects in the same sample. Importers usually apply 2.5 to major defects, the ones a customer would notice, and 4.0 to minor cosmetic defects. Lowering the AQL raises quality but also raises the chance a batch is rejected.

Is AQL the same as sampling by variables?

No. AQL under ISO 2859-1 uses single sampling plan by attributes: each unit is judged pass or fail against your checklist. Sampling by variables instead measures a value, such as weight or length, and analyzes the numbers statistically. AQL attribute sampling is the standard method for general product inspection.