AQL · Z1.4

AQL sampling plan calculator

Standard AQL sampling plan from ANSI Z1.4 / ISO 2859-1 Level II Normal Inspection. Lot size + AQL returns sample size and accept/reject thresholds.

Last updated 2026-05-09. Math runs in your browser, no data leaves your computer.

General guidance only, not legal or professional engineering advice. Verify against the cited primary sources (IMDG, REACH, ChAFTA, RCEP, Customs Tariff Act, supplier SDS, etc.) before committing to a shipment, declaration, or contract. Sourzi assumes no liability for outcomes based on these calculators.

AQL Z1.4 in chemical-trade audits

ANSI Z1.4 (formerly MIL-STD-105E) is the global standard for sample-based lot acceptance inspection. ISO 2859-1 mirrors it word-for-word. Buyers use the standard to inspect a manageable sample (32 to 200 units typically) instead of every unit in a lot, accepting or rejecting the whole lot based on the defects found in the sample.

Level II is the default inspection level for ongoing buyer-supplier relationships; it provides a reasonable balance between inspection cost and consumer risk. AQL 2.5 is the most-used acceptance level for chemical product attributes (visual defects, packaging integrity, label correctness). For critical attributes (purity, heavy metals, regulatory parameters), AQL 1.0 or even tighter (0.65, 0.40) is the right level; for non-critical (cosmetic), AQL 4.0 or 6.5 is acceptable.

The tool returns the code letter, sample size, and accept-reject thresholds for the chosen lot size and AQL. Apply the inspection plan to the lot, count defects in the sample, compare against the Accept / Reject thresholds for the lot decision.

Frequently asked

What is AQL?

Acceptable Quality Limit. The maximum percentage of defective units in a lot that the buyer will accept on average across many lots. AQL 1.0 = strictest (1% defective accepted on average); AQL 2.5 = standard for chemical and consumer goods; AQL 4.0 = lenient.

What is normal inspection level II?

The default ANSI Z1.4 inspection level. Higher levels (III, IV) increase sample size and reject more aggressively; lower levels (I) reduce sample size for trusted-supplier histories. Most buyer audits start at level II.

How do I read the result?

Inspect the sample size given. Count defects in the sample. If defects <= Accept (Ac), accept the lot. If defects >= Reject (Re), reject the lot. The numbers in between are not possible (Ac + 1 = Re).

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