AQL Calculator: Free Sample Sizes and Accept Reject Points

By Robert Low, Director, Lead Auditor & BRCGS Approved Trainer

Ask ten sites how they decided their sample size on goods in or finished product and you will get ten different answers. An AQL calculator takes the guesswork out. Give it a lot size and an AQL and it returns the sample size and the accept and reject numbers.

What the AQL Calculator Does

AQL stands for acceptable quality limit. It is the sampling approach behind most inspection plans, based on the standard sampling tables that have been used in industry for decades. You pick an inspection level, you pick an AQL for the type of defect, and the tables give you how many to check and how many defects you can tolerate before you reject the lot.

My free tool does the table lookup for you from the lot size and AQL, so you get a sample size and accept and reject points without flicking through a standard.

How to Use It

1. Open the AQL Calculator on the free resources page.
2. Enter the lot size.
3. Choose the AQL for the defect class you are inspecting.
4. Read off the sample size and the accept and reject numbers.
5. Record the result on your inspection sheet.

Where It Helps Beyond Certification

Outside of certification, this is a fairness tool. A documented sampling plan protects you when a customer disputes a batch, because you can show you inspected to an agreed method and not to someone’s gut feel. It also protects your suppliers from being rejected on a whim, which helps when you are building trust with them.

It works well alongside your supplier approval and goods in checks, and it gives your complaint investigations a baseline: what did we inspect, how many, and what was our accept number?

Where Sites Get Caught Out

AQL does not mean you are happy to ship that many defects. Critical defects, the ones that affect safety or legality, should be set at zero tolerance. Set your AQL by defect class: critical, major and minor, and write it down.