Incoming / Receiving Quality Control
AQL Sampling Plan Calculator
Determine sample size and acceptance/rejection numbers for a lot inspection, based on ANSI/ASQ Z1.4 (equivalent to ISO 2859-1), general inspection level II, single normal sampling.
What Is AQL Sampling?
Acceptable Quality Limit (AQL) sampling is a statistical method for inspecting a sample from a lot rather than 100% of units, while maintaining a defined statistical confidence that the lot's true defect rate is at or below an agreed threshold. It is widely used for incoming raw material and component inspection, and for finished product visual/packaging inspection.
How the Standard Works
ANSI/ASQ Z1.4 (and the equivalent ISO 2859-1) links three inputs to a sampling plan:
| Input | Role |
|---|---|
| Lot size | Determines the sample size code letter |
| Inspection level | Determines how the sample size scales with lot size (General Level II is the default for most applications) |
| AQL | The agreed maximum tolerable percent defective; determines Acceptance (Ac) and Rejection (Re) numbers |
The output is a sample size (n) and a pair of numbers: Ac (accept the lot if defects found ≤ this number) and Re (reject the lot if defects found ≥ this number).
Interactive Calculator
General inspection level II, normal (not tightened/reduced) inspection, single sampling plan.
Reading the Result
| Outcome | Action |
|---|---|
| Defects found ≤ Ac | Accept the lot |
| Defects found ≥ Re | Reject the lot |
| "R" shown for sample size | Use the next larger code letter's full sampling plan (arrow-down rule in the standard) |
This calculator implements the General Inspection Level II, Normal Inspection, Single Sampling table from ANSI/ASQ Z1.4 / ISO 2859-1 for common AQL values. For tightened/reduced inspection, special inspection levels (S-1 to S-4), or double/multiple sampling plans, consult the full standard tables. This tool is for educational and planning purposes — confirm your site's approved sampling plan before use in a GMP inspection decision.
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