AQL 2.5 Explained: What It Means for Your Shipment from China

January 2026 · 6 min read · Quality Control

If you buy from China, you will see "AQL 2.5" on every inspection quotation — but very few buyers actually understand what it does. This article explains it in plain English, with the exact numbers that matter.

What AQL means

AQL stands for Acceptable Quality Limit. It is not a promise that 2.5% of your goods will be defective. It is a sampling plan: the contract says "I accept a batch where the defect rate does not exceed 2.5% on major defects." The inspector samples a fixed number of units and decides pass or fail from that sample.

AQL 2.5 is the default used by most inspection companies worldwide for major defects. AQL 1.0 is stricter (used for premium products), AQL 4.0 is more lenient (commodity goods).

How the sampling works

Sampling follows the ISO 2859-1 (ANSI/ASQ Z1.4) tables. For a typical single-sampling plan at AQL 2.5, general inspection level II:

Note that the sample size barely grows after 3,000 units — a 10,000-piece order and a 3,000-piece order use nearly the same sample. That is by design: the risk being controlled is statistical, not proportional to order size.

The three defect classes

• Critical — unsafe, illegal, or could cause injury (e.g. exposed live wires, wrong plug for the market). One critical defect fails the entire batch.
• Major — likely to cause failure or return (e.g. a non-working function, badly chipped body). This is what the AQL 2.5 limit applies to.
• Minor — cosmetic, unlikely to affect use (e.g. a scuff on the underside). Often set at AQL 4.0.

How to use AQL in your contract

• Write it into the PO: "Inspection per AQL 2.5 major / 4.0 minor, ISO 2859-1, general level II, random sampling."
• Define critical defects for your product in writing — vague standards lead to disputes.
• Decide who pays for re-inspection after a fail (industry norm: supplier pays).
• Specify the inspection point (mid-production vs. pre-shipment) — they test different things.

Common mistakes buyers make

• Assuming AQL means "2.5% defects are fine" — it is a sampling plan, not a defect allowance.
• Letting the factory's own QC sign off with no independent party present.
• Not agreeing on the AQL level until after a problem appears — by then it is negotiation, not specification.