Quality calculator

AQL Sample Size Helper

Look up the AQL sampling plan for a lot: code letter, sample size and accept and reject numbers for general inspection levels I, II and III, single sampling, normal inspection.

Method note: Always follow the sampling instructions in the buyer quality manual. This helper does not replace the published standard.

Inputs

pcs

Inspection level

Buyers often specify different AQLs for critical, major and minor defects. Run the helper once for each.

Result

Sample size

125pcs

Accept (Ac)
7
Reject (Re)
8
Code letter
K

Accept the lot if 7 or fewer nonconforming units are found in the sample. Reject it if 8 or more are found.

Working
  1. Lot size 3,000 at level II -> code letter K (sample 125)
  2. At AQL 2.5: Ac 7, Re 8

Formula

Formula
Accept if d≤Ac,Reject if d≥Re\text{Accept if } d \le Ac, \quad \text{Reject if } d \ge Re

Accept the lot if defectives found ≤ Ac; reject if ≥ Re

SymbolMeaningUnit
dNonconforming units found in the samplepcs
Ac, ReAcceptance and rejection numberspcs

How the helper works#

The helper follows the single sampling plans for normal inspection used in the ISO 2859-1 and ANSI/ASQ Z1.4 family of tables:

  1. The lot size and inspection level give a code letter.
  2. The code letter gives the sample size.
  3. The AQL value gives the accept (Ac) and reject (Re) numbers, following the table's arrows where a plan points to another sample size.

See AQL in garment inspection for how the result is used.

Worked example#

Defaults: lot of 3,000 pieces, general level II, AQL 2.5.

  • Code letter K, sample size 125
  • Accept 7, reject 8

The inspector checks 125 pieces. Seven or fewer defective pieces in that class pass the lot; eight or more fail it. Run the helper again with AQL 4.0 for minor defects: the same lot gives Ac 10, Re 11.

Interpreting the result#

AQL sampling is a decision rule, not a quality level guarantee. Draw samples at random from across the lot, use the buyer's defect classes, and follow the buyer's manual where it differs from the standard tables. Record results on the AQL inspection sheet.

Assumptions

  • Single sampling plan, normal inspection, general inspection levels only (tightened, reduced and special levels S-1 to S-4 are not covered here).
  • Values follow MIL-STD-105E Tables I and II-A, which ANSI/ASQ Z1.4 and ISO 2859-1 share for this case.
  • Where the table points to another plan (an arrow), the plan below or above is used and its sample size replaces the code letter sample size.

Common errors

  • Keeping the code letter sample size after following an arrow in the table.
  • Selecting samples from one carton instead of randomly across the lot.
  • Treating AQL as the maximum defect rate a lot can have. It is a process average the plan is designed around.

Questions

Which inspection level should I use?

General level II is the usual default in garment inspection. Use the level stated in the buyer's manual.

What does an arrow in the table mean?

For some combinations of code letter and AQL, the standard tables point to a different sample size. The helper follows that rule and shows when the plan letter differs from the code letter.

Does the helper support special levels S-1 to S-4?

No. It covers general levels I, II and III. Use the full tables for special levels.

Related formulas

Guides for this calculation

Quality & DefectsGuide3 min read

AQL in Garment Inspection: Sampling Plans Explained

AQL sampling decides how many garments to inspect from a lot and how many defects are allowed. How the sampling tables work, inspection levels, code letters, accept and reject numbers, and what AQL does and does not guarantee.

Quality & DefectsHow-to3 min read

Final Inspection of Garments: How a Pre-Shipment Inspection Works

A final (pre-shipment) inspection checks a finished, packed lot against the buyer's requirements before it ships. What is checked, how samples are drawn, the order of work, and how to prepare so the lot passes the first time.

Quality & DefectsHow-to3 min read

Inline Inspection in Sewing Lines: Catch Defects at the Source

Inline inspection checks work at or near each operation while the line is running. How the traffic light system works, how to choose operations to check, sample sizes and frequency, and how to act on the results.

Quality & DefectsGuide3 min read

DHU (Defects per Hundred Units): Formula and How to Use It

DHU counts defects per hundred garments checked. The formula, how it differs from defective percentage, a worked example from end-of-line checking, and how to turn DHU data into action on the line.

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