Free AQL Calculator
Sample Size & Acceptance Numbers
Calculate sample size and acceptance/rejection numbers instantly using ISO 2859-1 ANSI/ASQ Z1.4 standard. Perfect for garment, textile, and product quality inspection. Get accurate sampling plans for critical, major, and minor defects in seconds.
Inspection Parameters
AQL Limits by Defect Type
Industry standard for garments: Critical 0, Major 2.5, Minor 4.0 at General Level II
Inspection Results
What This Means
Enter your lot quantity and inspection parameters to see sample size requirements. The calculator will show how many units to inspect and the acceptance/rejection numbers for each defect type.
What is Acceptable Quality Limit (AQL)?
Acceptable Quality Limit (AQL) is a statistical sampling method defined by the international standard ISO 2859-1 (also known as ANSI/ASQ Z1.4 in the United States). It determines how many units from a production lot should be randomly inspected and the maximum number of defective units allowed before the lot is rejected. AQL sampling is the cornerstone of modern quality control inspection used by importers, retailers, brands, and third-party inspection companies worldwide to make objective, data-driven accept/reject decisions on manufactured goods.
Instead of inspecting 100% of products (which is prohibitively expensive and time-consuming for large production runs), AQL sampling achieves statistically comparable confidence with a fraction of the units inspected typically between 80 and 315 units for common lot sizes. This saves significant time and cost while still protecting buyers from shipping defective goods.
Three Types of Defects in AQL Sampling
Critical Defects (AQL 0.0–0.65%)
Defects that pose a safety hazard or violate mandatory regulations. Examples include sharp edges on children's toys, electrical hazards, or toxic materials. Critical defects typically use AQL 0.0, meaning zero tolerance any critical defect found results in lot rejection.
Major Defects (AQL 1.0–2.5%)
Defects that affect the product's function or usability. Examples include a zipper that doesn't close, a motor that doesn't start, or incorrect labeling. The industry standard for major defects is AQL 2.5.
Minor Defects (AQL 2.5–4.0%)
Cosmetic imperfections that do not affect the product's function. Examples include slight color variation, minor scratches, or loose threads. The standard for minor defects is AQL 4.0.
How AQL Calculation Works
Example: 5,000 Garment Order
For a lot of 5,000 units at General Inspection Level II, look up Table A. The lot range 3,201–10,000 with Level GII gives code letter "L".
Code letter "L" in Table B shows a sample size of 200 units. This means you inspect 200 randomly selected garments from the 5,000-unit lot.
For AQL 2.5 (Major defects), code letter L shows Ac=10, Re=11. This means if you find 10 or fewer major defects, the lot passes. If you find 11 or more, it fails.
Critical defects always use Ac=0, Re=1 (zero tolerance). For AQL 4.0 (Minor defects), code letter L shows Ac=14, Re=15.
After inspecting 200 units, count actual defects found. Compare against each Ac/Re threshold. If any defect type exceeds its Re number, the entire lot is rejected or requires 100% inspection.
Frequently Asked Questions
AQL (Acceptable Quality Limit) is the maximum percentage of defects considered acceptable in a production batch. It's a statistical sampling method defined by ISO 2859-1 and ANSI/ASQ Z1.4 standards used worldwide for quality control in manufacturing.
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 balances quality assurance with practical inspection costs for apparel production.
Ac (Acceptance number) is the maximum number of defects allowed for the lot to pass. Re (Rejection number) is the minimum number of defects that causes the lot to fail. For example, Ac=10, Re=11 means 10 or fewer defects pass, 11 or more fail.
Special inspection levels (S-1 to S-4) are used for small samples or destructive testing. General levels I, II, and III are for normal inspection, with Level II being the standard. Level I requires smaller samples (less strict), Level III requires larger samples (more strict).
Consider defect severity and your quality requirements. Critical defects (safety issues) should always use AQL 0. Major defects affecting function typically use AQL 1.5–2.5. Minor cosmetic issues often use AQL 4.0–6.5. Your buyer's requirements and industry standards should guide your choice.
When a lot fails AQL inspection, common actions include: 100% inspection of the entire lot to remove defective units, rework to fix defects, shipment rejection, or negotiating with the supplier. The action depends on your contract and the severity of quality issues.
This calculator implements the ISO 2859-1 / ANSI/ASQ Z1.4 standard, which is used across manufacturing industries including textiles, electronics, automotive, and pharmaceuticals. While the standard is universal, different industries may prefer specific AQL combinations.
AQL 2.5 means the acceptable quality limit is set at 2.5%. This is the most commonly used AQL value for general consumer products and is the industry standard for major defects in pre-shipment inspections. With AQL 2.5, a lot is statistically expected to contain no more than 2.5% defective units. It strikes a balance between quality assurance and practical inspection costs.
After inspecting the specified sample size, count the total number of defective units found. If the count is equal to or less than the Accept number (Ac), the lot passes inspection. If the count is equal to or greater than the Reject number (Re), the lot fails. For example, with Ac = 3 and Re = 4, finding 3 or fewer defects means the lot is accepted; 4 or more means it is rejected.
General Inspection Level II is the default and most widely used level. Level I requires fewer samples (less discrimination) and is used when lower inspection costs are needed or the process is well-established. Level III requires more samples (higher discrimination) and is used when stricter quality assurance is required, such as for safety-critical products. The higher the level, the larger the sample size and the greater the statistical confidence in the result.
No. AQL is a statistical sampling method where only a randomly selected portion of the lot is inspected. It provides a high confidence level that the lot meets quality requirements without inspecting every unit. 100% inspection checks every single unit and is typically reserved for critical safety items or very small lot sizes. AQL sampling is far more cost-effective for large production runs.
Special Inspection Levels (S-1, S-2, S-3, S-4) are used when very small sample sizes are needed, typically for destructive testing where inspected units cannot be sold, or for expensive products where minimizing sample size is important. S-1 uses the smallest sample and S-4 the largest among special levels. These levels provide lower statistical discrimination than general levels but are appropriate when testing is costly or destructive.