AQL Sampling Plan Calculator

Enter Inspection Details

Product name

Lot reference

Inspector

Lot size

Inspection level

Inspection severity

AQL percent

Expected defective percent

RQL or LQ percent

Probability model

Manual sample size

Actual defects found

Inspection notes

Formula Used

The calculator first assigns a code letter from lot size and inspection level. The code letter gives the base sample size. If a manual sample size is entered, that value is used instead.

Binomial probability of accepting a lot: P(accept) = Σ C(n,x) p^x(1-p)^n-x, for x from 0 to c. Here, n is sample size. The value c is the accept number. The value p is the defect probability.

Poisson approximation: P(accept) = Σ e^-λλ^x / x!, where λ equals n times p.

Producer risk equals 1 - P(accept at AQL). Consumer risk equals P(accept at RQL or LQ). Average outgoing quality equals p × P(accept) × (1 - n / lot size).

How to Use This Calculator

Enter the total lot size.
Select the inspection level.
Enter the AQL percentage from your quality agreement.
Add the expected defect rate and RQL value.
Choose binomial or Poisson probability.
Enter actual defects if inspection is already complete.
Press calculate to view the result above the form.
Download CSV or PDF for inspection records.

Example Data Table

Lot Size	Level	AQL	Code Letter	Sample Size	Typical Use
500	II	2.5%	H	50	General incoming check
1,200	II	1.0%	J	80	Finished goods inspection
10,000	III	0.65%	M	315	Higher risk shipment
50,000	S-3	4.0%	G	32	Small destructive test

About the AQL Sampling Plan Calculator

An AQL sampling plan helps quality teams inspect a lot without checking every unit. AQL means acceptable quality limit. It defines the defect rate that a buyer can usually accept for normal production. This calculator turns lot size, inspection level, and AQL into a practical sample plan. It also estimates acceptance risk, rejection risk, and expected outgoing quality. Review the plan again whenever suppliers, materials, or tolerance rules change.

Why Sampling Plans Matter

Full inspection can be slow, costly, and still imperfect. Sampling gives a controlled way to decide if a shipment should pass. The method is useful for factories, importers, warehouses, and service teams. It creates clear limits before inspection begins. This reduces arguments after defects are found. It also supports better supplier records.

How This Tool Works

The tool first finds a code letter from the lot range and inspection level. It then converts that letter into a sample size. The sample size is never allowed to exceed the lot quantity. Next, it calculates an accept number. A lot passes when found defects are equal to or below that number. It fails when defects reach the reject number.

Risk and Probability View

AQL plans do not guarantee perfect lots. They control probability. The producer risk shows the chance of rejecting a lot that is near the selected AQL. The consumer risk shows the chance of accepting a lot at the entered limiting quality level. The probability of acceptance curve helps users compare strict and relaxed settings.

Best Use Cases

Use this calculator before a receiving inspection, final product check, or vendor audit. Pick the inspection level that matches risk and product value. Level II is common for general checks. Level III gives a larger sample. Special levels use smaller samples for destructive tests or expensive checks. Always keep product standards, contracts, and safety needs in mind.

Reading the Result

The result table shows the code letter, sample size, accept number, reject number, and estimated risks. Use the status line when actual defects are entered. Export the report as CSV or PDF for records. Save the output with purchase orders, lot numbers, and inspection notes. This gives your team a repeatable decision trail.

FAQs

What does AQL mean?

AQL means acceptable quality limit. It is the defect level that can be accepted for a lot under a chosen sampling plan.

Is this the same as full inspection?

No. Sampling checks only selected units. It estimates lot quality through probability, while full inspection checks every available unit.

Which inspection level should I choose?

Level II is common for general use. Level I checks fewer units. Level III checks more units and gives stricter evidence.

What is an accept number?

The accept number is the highest allowed defect count in the sample. The lot passes when defects are equal to or below it.

What is a reject number?

The reject number is the defect count that fails the lot. It is usually one more than the accept number.

When should I use Poisson approximation?

Use it for quick estimates when the defect rate is low and the sample is large. Binomial is better for direct sample probability.

Can I enter my own sample size?

Yes. Use the manual sample field. The calculator will keep the sample size within the entered lot quantity.

Does this replace official standards?

No. It supports planning and estimation. Use your contract, customer rules, or official inspection standard for final compliance.