AQL Calculator
New to AQL? No problem. This calculator guides you step-by-step to determine how many units to inspect and what pass/fail criteria to use.
Calculate Your Sampling Plan
Your Sampling Plan
Here's what you need to inspect
YOUR INSPECTION PLAN
Sample Size Code Letter
ISO 2859-1 code
Units to Inspect
What to do next
- Share this plan with your quality inspector or supplier
- Randomly select the required number of units from your production batch
- Inspect each unit and categorise any defects found (Critical/Major/Minor)
- Compare defect counts against the Ac/Re numbers to accept or reject the lot
Understanding AQL Sampling
Everything you need to know about acceptance quality limits
What is AQL?
AQL (Acceptance Quality Limit) is a statistical threshold that defines the maximum proportion of defects considered acceptable in a batch. Rather than inspecting every single unit, a representative sample is drawn and examined. Based on the number of defects found in that sample, the entire lot is either accepted or rejected.
This approach balances quality assurance with practical efficiency, allowing manufacturers and buyers to make informed decisions without the cost and time of 100% inspection.
Why AQL matters
- Balances quality with efficiency: Inspection costs are kept reasonable whilst maintaining quality standards.
- Objective pass/fail criteria: Removes subjectivity and provides clear, defensible quality gates.
- Industry standard: Based on ISO 2859-1 / ANSI/ASQ Z1.4, recognised globally across sectors.
- Risk management: Quantifies acceptable risk levels for both buyer and supplier.
Understanding defect types
Critical Defects
Safety hazards, legal non-compliance, or issues that could cause injury. Usually zero tolerance (AQL 0.0).
Major Defects
Functional or appearance defects that most customers would reject. Typical AQL: 1.0–2.5%.
Minor Defects
Small cosmetic issues that don't affect function. Typical AQL: 2.5–4.0%.
Frequently Asked Questions
I'm new to AQL. Where do I start?
Start simple! Just fill in three things:
- Your lot size (how many units you're producing)
- Keep "General II" selected (it's the standard)
- Use our recommended AQL values: Critical 0, Major 2.5, Minor 4.0
The calculator will tell you exactly how many units to inspect and what the pass/fail criteria are.
Do I have to inspect every single unit?
No! That's the whole point of AQL sampling. You inspect only a statistically representative sample (for example, 125 units from a batch of 5,000), then make a decision about the entire lot. This saves massive amounts of time and money whilst still providing reliable quality assurance.
What does "Ac" and "Re" mean?
Ac (Acceptance number): The maximum number of defects allowed to pass. If you find this many or fewer defects, the lot passes.
Re (Rejection number): If you find this many or more defects, the lot fails.
Example: If Ac=7 and Re=8 for Major defects, finding 7 major defects means PASS, but finding 8 or more means FAIL.
What if I find a critical defect?
Reject the lot immediately. Critical defects pose safety or legal risks and typically have AQL 0.0 (zero tolerance). Finding even one critical defect means the entire batch fails. Work with your supplier to identify root causes and implement corrective actions before resubmitting.
Can I change my AQL levels later?
Yes. AQL levels are defined in your purchase agreements or quality specifications and can be adjusted as your risk tolerance, product maturity, or supplier performance changes. Document any changes clearly and communicate them to your supplier before inspection.
Is AQL the same as a pass rate or quality target?
No. AQL is a statistical acceptance threshold for sampling inspection, not a quality goal. It defines the maximum percentage of defects that can be considered acceptable for accepting or rejecting a lot, but it's not an endorsement of that defect level. Always aim for zero defects in production; use AQL to make practical inspection decisions.