AQL 1.0 vs 2.5 vs 4.0: Sample Size, Accept/Reject Numbers and How to Choose

AQL 1.0, 2.5, or 4.0 — pick the wrong one and you either pay for a standard you don't need, or you accept a bad batch that should have failed. Pick it right and one line in your PO settles every quality argument before production starts. 🔍

We run hundreds of China inspections a month, and the most common mistake we see isn't skipping AQL entirely. It's copying a friend's AQL number without knowing what it actually allows. This guide breaks down what each level means, the exact sample sizes and accept/reject numbers, and how to choose the right one for your product. 📊

What AQL 1.0, 2.5 and 4.0 actually mean

AQL stands for Acceptable Quality Limit. The number is the maximum percentage of defective units you're willing to accept in a batch. AQL 1.0 accepts up to 1.0% defects. AQL 2.5 accepts up to 2.5%. AQL 4.0 accepts up to 4.0%.

Important: you don't inspect every unit. You check a statistically valid sample, count the defects, and judge the whole batch on it. The AQL number becomes two numbers on your report: Ac (accept) and Re (reject). If defects in the sample are at or below Ac, the batch passes. At or above Re, it fails.

Lower AQL = stricter. Here's the simple version:

Sample sizes for AQL 1.0, 2.5 and 4.0 (level II)

Here's the part importers get wrong: the sample size does not depend on the AQL level. It depends on your lot size. The AQL level only changes the accept/reject numbers on that sample.

At general inspection level II, this is the table we use every day:

Read it like this: a 5,000-unit order sits in the 3,201 – 10,000 row. Code letter L. Sample 200 units. At AQL 1.0 the batch passes at 5 or fewer defects and fails at 6. At AQL 2.5 it passes at 10 and fails at 11. At AQL 4.0 it passes at 14 and fails at 15. Same sample, very different risk. 📐

How to choose between AQL 1.0, 2.5 and 4.0

Ask one question per product: what happens if a defective unit reaches the customer?

• AQL 1.0 — the defect hurts your customer or your margin badly. Electronics that can fail, kids' toys with safety rules, anything with a certification requirement. One bad unit can trigger a review, a return, or worse.
• AQL 2.5 — the default. Apparel, home decor, most FBA consumer goods. Defects exist but the customer impact is manageable.
• AQL 4.0 — defects are cosmetic or the product is low-risk. Packaging scratches, off-color threads, simple tools. Or use it for minor defects while major defects run at 2.5.

A practical setup most importers use: AQL 2.5 for major defects, AQL 4.0 for minor defects. Critical defects (safety, legality, function) always run at AQL 0 — zero tolerance. This is how the defect classification works in a real inspection report.

Whatever you pick, put it in writing before production. If you don't set the standard, the factory sets it for you — and it won't be 2.5. This is the single most common mistake we see across hundreds of inspections a month. ✍️

Real inspection: the AQL level decided the outcome

A lighting importer ordered 8,000 LED panels and told the factory "quality same as the sample." No AQL in the PO. The factory produced in a hurry, and our inspector checked 315 units (code M, AQL 2.5): 23 had wrong inner print, 11 had cracked edges. 34 defects total against an accept number of 21 — the batch failed. ❌

The seller renegotiated from leverage: the factory reworked all 8,000 units at their cost, and the shipment left 9 days late but clean. The whole fix cost the factory about $4,000. If it had shipped as-is, the seller's return rate would have eaten that in Amazon fees alone — plus the listing's rank. The difference between "sample looked good" and "batch passed AQL" is one line in the PO. 📝

Now flip it: had that importer set AQL 4.0 because "everyone uses 4.0," the same 34 defects on 315 units would still have failed (reject at 22), so it holds either way — but on a smaller lot the gap between 1.0 and 4.0 is exactly where bad batches slip through. Know your number before you sign.

Run the numbers yourself

Use the free AQL sample size calculator — enter your batch size, pick inspection level II, set your AQL for major and minor defects, and get your sample size and Ac/Re numbers in seconds. No login needed. If you'd rather have an inspector handle it, every CloudSpects inspection applies the official AQL tables and reports the Ac/Re result in your photo report — from $169/man-day.

Deeper on AQL? Start with the AQL 2.5 answer pack, then how to calculate sample size, and how to read the AQL chart.

Frequently asked questions

What is the difference between AQL 1.0, 2.5 and 4.0?

Lower AQL numbers are stricter. AQL 1.0 allows the fewest defects and is used for electronics, safety-critical products and children's goods. AQL 2.5 is the default for most consumer goods. AQL 4.0 allows the most defects and suits minor cosmetic defects or low-risk items. For a 5,000-unit lot at level II, AQL 1.0 passes at 5 or fewer defects in a 200-unit sample, AQL 2.5 passes at 10, and AQL 4.0 passes at 14.

What does AQL 1.0 mean?

AQL 1.0 means you accept up to 1.0% defective units in the batch. In practice it works through the sampling table: for a 5,000-unit lot at general inspection level II, the inspector checks 200 units and the batch passes if 5 or fewer are defective, and fails at 6 or more. AQL 1.0 is used for electronics, safety products and children's goods.

What does AQL 4.0 mean?

AQL 4.0 means you accept up to 4.0% defective units in the batch. For a 5,000-unit lot at level II, the inspector checks 200 units and the batch passes if 14 or fewer are defective, and fails at 15 or more. AQL 4.0 suits minor cosmetic defects, packaging issues and low-risk products.

Which AQL level should I use for my product?

AQL 2.5 at general inspection level II is the default for most consumer goods. Use AQL 1.0 for electronics, children's products or anything safety-critical, and AQL 4.0 for minor cosmetic defects or low-risk items. Many importers set AQL 2.5 for major defects and AQL 4.0 for minor defects. Get the standard in writing before production starts.

How many units does the inspector check for AQL 1.0, 2.5 or 4.0?

The sample size comes from the lot size, not the AQL level. At general inspection level II, a 3,201-10,000 unit lot gets code letter L and a 200-unit sample; a 10,001-35,000 unit lot gets code letter M and a 315-unit sample. The AQL level only changes the accept/reject numbers on that sample.

Is AQL 1.0 stricter than AQL 4.0?

Yes. AQL 1.0 rejects a batch at far fewer defects than AQL 4.0. On a 200-unit sample (5,000-unit lot at level II), AQL 1.0 fails at 6 defects, AQL 2.5 fails at 11, and AQL 4.0 fails at 15. A stricter AQL means more rework and more supplier pushback, so pick the level that matches the real risk of the product.

Last updated: August 2026. AQL tables follow ANSI/ASQ Z1.4 / ISO 2859-1 general inspection level II. Prices and turnaround times based on standard service levels.

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