What is AQL in quality inspection?

AQL (Acceptable Quality Level) is the maximum percentage of defective units a buyer will accept in a sample. AQL 2.5 means up to 2.5% major defects are tolerated. It defines the pass/fail threshold for statistical sample inspection per ISO 2859-1.

What AQL level should importers use?

Most buyers use AQL 0 for critical defects, AQL 2.5 for major defects, and AQL 4.0 for minor defects at General Inspection Level II. Tighten to Level III (or AQL 1.5) for new suppliers, high-value goods, or after a failed inspection.

How is AQL sample size calculated?

Sample size is derived from the ISO 2859-1 table using lot size and inspection level. For a 3,000-unit lot at Level II, you inspect 125 units. The acceptance number (Ac) tells you the maximum defects allowed before the lot fails.

What is the difference between AQL 2.5 and AQL 4.0?

AQL 2.5 is stricter (fewer defects allowed) and used for major defects that affect function or salability. AQL 4.0 is more lenient and used for minor cosmetic defects that don't impact use, like minor scratches or loose threads.

Can AQL replace 100% inspection?

Yes for most consumer goods. AQL provides statistical confidence with a fraction of the cost of full inspection. 100% inspection is only used for safety-critical components (medical, automotive) or extremely high-value items.

Quality Control April 2026

AQL Inspection: Levels, Sampling & the AQL 2.5 Chart (2026)

A complete guide to AQL inspection — Acceptable Quality Level, the international standard (ISO 2859-1) for product inspection sampling. Learn AQL inspection levels I/II/III, sample sizes, accept/reject numbers, and how to set AQL 2.5 for imports from India.

12 min read

What is AQL?

AQL (Acceptable Quality Level) is a statistical sampling system defined in ISO 2859-1 (international) and ANSI/ASQ Z1.4 (US). It determines how many units to randomly inspect from a production lot and the maximum number of defects allowed for the shipment to pass.

AQL is the global standard used by importers, retailers, and inspection companies. It doesn't mean you accept defects — it means you define your acceptable tolerance and use statistics to make a reliable pass/fail decision without inspecting every single unit.

Inspection Levels

Level I (Reduced)

Sample size: Fewer samples

Best for: Established suppliers with proven track record

Higher risk of missing defects

Level II (Normal)

Sample size: Standard samples

Best for: Most common — default for routine inspections

Balanced risk and cost

Level III (Tightened)

Sample size: More samples

Best for: New suppliers, high-value products, or after failures

Lowest risk, highest inspection cost

Defect Classification & AQL Values

Critical (AQL 0)

Defects that pose safety hazards or violate regulations. Zero tolerance — any critical defect fails the inspection.

Examples: Sharp edges on children's products, toxic chemicals, electrical safety failures

Major (AQL 2.5)

Defects likely to result in product failure or customer returns. Affects function, appearance, or salability.

Examples: Wrong colour, broken zipper, missing components, holes in fabric

Minor (AQL 4.0)

Defects that don't affect function but are noticeable. Customer may still accept the product.

Examples: Slight colour variation, minor scratch, loose thread, small stain

AQL Sample Size Chart (General Level II)

Lot Size (units)	Sample Size
2–8	2
9–15	3
16–25	5
26–50	8
51–90	13
91–150	20
151–280	32
281–500	50
501–1,200	80
1,201–3,200	125
3,201–10,000	200
10,001–35,000	315
35,001–150,000	500

This chart shows General Inspection Level II — the most commonly used level. For the accept/reject numbers at each AQL value, refer to the full ISO 2859-1 tables or use our inspection team who apply these standards automatically.

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