AQL Calculator: Sample Size & Accept/Reject Numbers

AQL (Acceptable Quality Limit) is the maximum percentage of defects considered acceptable in a production batch. It is a statistical sampling method defined by ISO 2859-1 and ANSI/ASQ Z1.4 standards used worldwide for quality control in manufacturing, garment, and textile industries. Rather than inspecting every unit, AQL determines how many units to check and how many defects the entire lot can have before it is rejected.

The garment industry standard is: Critical defects AQL 0 (zero tolerance), Major defects AQL 2.5, and Minor defects AQL 4.0, using General Inspection Level II. This combination is specified by most international buyers sourcing from Bangladesh, China, Vietnam, and other manufacturing countries, and is used by third-party inspection companies as the default unless a buyer specifies otherwise.

Ac (Acceptance number) is the maximum number of defective units found in the sample that allows the entire lot to pass inspection. Re (Rejection number) is the minimum count that causes the lot to fail. The two numbers are always consecutive — for example, Ac=10 and Re=11 means finding exactly 10 defects passes the lot, while finding 11 fails it. There is no gray zone between them.

ISO 2859-1 defines seven inspection levels: four Special levels (S-1, S-2, S-3, S-4) and three General levels (I, II, III). Special levels use very small sample sizes and are suitable for destructive testing or costly inspections where minimizing sample size matters most. General Level II is the standard for the majority of commercial inspections. General Level I uses smaller samples and is less discriminating. General Level III uses larger samples and provides greater statistical confidence. Unless your buyer or contract specifies otherwise, always use General Level II.

The right AQL depends on the severity of potential defects and your buyer's requirements. Any defect that could harm the end user should be treated as critical with AQL 0. Defects that would cause a consumer to return the product or make it unsellable — wrong size, broken hardware, major stitching failure — typically use AQL 1.5 to 2.5. Cosmetic issues that reduce perceived quality but do not affect use typically use AQL 4.0. Always check your purchase order or buyer's quality manual first, as many brands specify AQL requirements directly.

When a lot fails AQL inspection, the typical response depends on your contract and the severity of defects. Common actions include: performing 100% inspection of the entire lot to sort and remove all defective units; reworking defective pieces and re-submitting the lot for reinspection; rejecting the shipment and requiring the supplier to reproduce or replace the goods; or negotiating a price reduction or corrective action plan. A failed inspection does not automatically mean the entire lot is scrapped — it means the lot requires action before it can ship.

Yes. This calculator implements the ISO 2859-1 / ANSI/ASQ Z1.4 standard, which is the universal sampling standard used across garment, textile, electronics, toys, automotive parts, pharmaceuticals, food packaging, and virtually every manufacturing sector. While the AQL values and defect definitions differ by industry and product type, the underlying sampling tables and code letter logic are identical. The calculator is product-agnostic — input any lot size and AQL combination and it will give you the correct result.

AQL 2.5 is the most widely used AQL value in global manufacturing and is the industry standard for major defects in garment and consumer goods inspections. It means the sampling plan is calibrated to accept lots where the true defect rate is at or below 2.5%. For a 5,000-unit lot at General Level II, AQL 2.5 translates to inspecting 200 units with an acceptance number of 10 — meaning up to 10 defective units in the sample are acceptable before the lot is rejected. AQL 2.5 strikes the practical balance between quality protection and realistic production variance.

After inspecting the sample, count all defective units found. Compare this count to the Ac and Re numbers. If your count is equal to or less than Ac, the entire lot passes. If it equals or exceeds Re, the entire lot fails. For example, if Ac=7 and Re=8: finding 7 or fewer defects means the lot passes; finding 8 or more means it fails. Defects are counted per unit — if one garment has two separate major defects, it counts as one defective unit for the purposes of the major defect tally (though some buyers count total defects rather than defective units — always confirm which method your buyer requires).

General Level II is the default and provides a balanced sample size suitable for most commercial inspections. Level I uses a smaller sample size — roughly half of Level II — and provides less statistical discrimination. It is appropriate for routine inspections of well-established products where the cost of inspection needs to be minimized and the supplier has a good quality track record. Level III uses a larger sample size — roughly double Level II — and offers higher statistical confidence in the result. It is used for critical products, safety-sensitive categories, or when a supplier's quality has been inconsistent and a buyer wants stronger assurance before accepting a shipment.

No, AQL sampling and 100% inspection are fundamentally different approaches. AQL sampling inspects a statistical subset of the lot — typically 5% to 15% of units depending on lot size — and uses the result to make an inference about the entire lot's quality. It is fast and cost-effective. 100% inspection checks every single unit and physically removes or tags every defective piece. It is used for critical safety products, very small lots, or as a corrective action after a lot fails AQL sampling. For large garment production runs, 100% inspection is impractical and unnecessary when a well-calibrated AQL sampling plan is in place.

Special Inspection Levels S-1, S-2, S-3, and S-4 are designed for situations where inspecting large numbers of units is impractical or destructive. S-1 uses the smallest sample size of the four. They are most commonly used for performance testing such as wash fastness, tensile strength, or flammability testing — where each tested unit is destroyed or significantly damaged in the process. Using a special level for regular visual inspection of finished garments is not appropriate; General Level II is the correct choice for that purpose.

Bangladesh garment factories exporting to buyers in the USA, UK, EU, Canada, and Australia routinely conduct pre-shipment AQL inspections as a condition of the purchase order. The standard inspection criteria are Critical 0, Major 2.5, Minor 4.0 at General Level II. Third-party inspection companies visit factories in Dhaka, Gazipur, Narayanganj, and Chittagong to conduct random sampling inspections before cargo is loaded for export. Buyers use the inspection report to make the final shipment approval or hold decision. For factories in Bangladesh, maintaining consistent AQL compliance is directly tied to buyer confidence, repeat orders, and long-term sourcing relationships.