ANSI/ASQ Z1.4 / ISO 2859-1

AQL Sample Size Calculator

Normal inspection, single sampling, client-side table lookup with Table I code letters and Table II-A arrow resolution.

Inputs

File-safe, deterministic
Inspection type

Sampling plan

-

Ready
Code letter -
Sample size -
Accept -
Reject -

Enter a lot size to calculate the plan.

Level -
Input code -
Resolved code -
Table II-A cell -

Lookup table

Current row and AQL result
Lot range S-1 S-2 S-3 S-4 I II III

Current code across AQLs

Direct cells and arrow targets
AQL Cell Resolved code n Ac Re

Self-tests

Golden checks run locally against the encoded tables.

About the AQL Sample Size Calculator (ANSI/ASQ Z1.4)

Determining how many units to inspect in a production batch is critical for maintaining quality control without wasting resources. Calculating the AQL sample size helps quality inspectors identify the precise number of items to test and the acceptable number of defects. This approach ensures suppliers and buyers agree on statistically valid acceptance criteria based on standard inspection levels.

How it works

  1. Select the total lot or batch size being produced or received.
  2. Choose the general inspection level (typically Level II for standard inspections).
  3. Set the Acceptable Quality Limit (AQL) percentages for critical, major, and minor defects.
  4. Note the required sample size and the specific Accept/Reject (Ac/Re) criteria.

Frequently asked questions

What does General Inspection Level II mean?

Level II is the standard default level used for most normal sampling under ANSI/ASQ Z1.4, providing a balanced trade-off between inspection cost and defect risk.

How do I choose the right Acceptable Quality Limit?

Typical consumer goods use AQLs of 0.0 for critical defects, 2.5 for major defects, and 4.0 for minor defects, but medical or automotive components require much stricter limits.

What is the difference between Ac and Re numbers?

The Accept (Ac) number is the maximum number of defective units allowed in the sample to pass the lot, while the Reject (Re) number is the threshold that causes the entire lot to fail.

Does this calculator use single or double sampling plans?

This specific calculation uses normal single sampling plans, which means the accept/reject decision is made after inspecting a single sample group drawn from the lot.

References