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AQL sampling plan calculator (ISO 2859-1)
Find the sample size and the accept and reject numbers for incoming inspection from the lot size, the inspection level and the AQL, following ISO 2859-1 and ANSI/ASQ Z1.4 single sampling for normal inspection.
The operating characteristic curve shows how likely a lot is to be accepted at each defect rate, so you can see the real protection of the plan.
01Method
Enter the lot size, choose the inspection level and the AQL. The tool finds the code letter, the sample size n, the acceptance number Ac and the rejection number Re. Enter the number of nonconforming units found to get the accept or reject decision.
The OC curve and the LTPD (the defect rate accepted only 10 % of the time) show what quality level the plan really guarantees.
02When to use it
Use AQL sampling for incoming inspection of purchased parts, for final inspection of lots before shipment, and for audits of finished goods in consumer products and electronics. It reduces inspection effort compared with 100 % inspection while giving a documented, standard decision rule that suppliers and customers accept.
For safety-critical characteristics, sampling alone is not enough; control them at the source with capability and error-proofing.
The tool covers lot sizes from 2 to over 500,000 units, the general inspection levels I, II and III and the special levels S-1 to S-4 for destructive or expensive tests. Record the number of nonconforming units found and the decision is documented on the PDF, which gives a traceable incoming inspection record for every delivery.
PDF report in one click
Export the sampling plan with your header (part, supplier, lot) and logo as a PDF, including the decision and the OC curve, for the incoming inspection record.
Private: runs in your browser
The calculation runs in your browser. Supplier and lot information stays on your computer.
How it works
- The lot size and inspection level give the sample size code letter (ISO 2859-1 Table 1).
- The code letter and AQL give the sample size and Ac / Re in the master table (Table 2-A, normal inspection).
- The OC curve shows how likely a lot with a given percent defective is to be accepted.
The plans are checked against reference values from ISO 2859-1, see the validation report. Switching rules to tightened or reduced inspection are not applied automatically: see ISO 2859-1 switching rules for when to switch. To decide how many parts you need for other purposes, use the sample size calculator.
Frequently asked questions
›What does AQL mean?
Acceptable quality limit: the worst process average (percent nonconforming) that is still considered acceptable for sampling inspection. An AQL of 1.0 does not mean 1 % defects are acceptable in your product, it is a parameter of the sampling plan.
›What sample size and Ac / Re apply for AQL 0.65?
With general inspection level II, normal inspection, single sampling (ISO 2859-1 / ANSI Z1.4): lot 91–280: n = 20, Ac 0, Re 1 (code letter G follows the arrow up to F). Lot 281–1,200: n = 80, Ac 1, Re 2 (code letter H follows the arrow down to J). Lot 1,201–3,200: n = 125, Ac 2, Re 3. Lot 3,201–10,000: n = 200, Ac 3, Re 4. Lot 10,001–35,000: n = 315, Ac 5, Re 6. AQL 0.65 is a common level for major defects. Enter your lot size above to get the exact plan and its OC curve.
›Which inspection level should I use?
General inspection level II is the default. Level I uses smaller samples, level III larger ones. Special levels S-1 to S-4 are for destructive or expensive tests where small samples are needed.
›What do Ac and Re mean?
Ac is the acceptance number: accept the lot if the number of nonconforming units in the sample is at most Ac. Re is the rejection number: reject if it is Re or more.
›What do the arrows in the AQL table mean?
Some combinations of code letter and AQL have no plan in the table, only an arrow. You then use the first plan below or above the arrow, with its sample size. The tool follows the arrows automatically and tells you when it did.
›Is AQL sampling acceptable in automotive?
Many automotive customers require zero defects and do not accept AQL plans with acceptance numbers above 0. Use AQL sampling for incoming inspection where agreed, and statistical process control for your own processes.