[Guide] AQL Inspection Cheat Sheet: How to Use Statistical Sampling for FBA Shipments

What Is AQL?

AQL (Acceptable Quality Limit) is the maximum number of defective units allowed in a sample before an entire shipment is rejected. It is governed by the international ANSI/ASQ Z1.4 standard.

Quick Reference: Common AQL Sample Sizes (General Level II)

|Lot Size|Code Letter|Sample Size|AQL 2.5 (Accept / Reject)|AQL 1.0 (Accept / Reject)|

|:-|:-|:-|:-|:-|

|2 – 8|A|2|0 / 1|0 / 1|

|9 – 15|B|3|0 / 1|0 / 1|

|16 – 25|C|5|0 / 1|0 / 1|

|26 – 50|D|8|0 / 1|0 / 1|

|51 – 90|E|13|1 / 2|0 / 1|

|91 – 150|F|20|2 / 3|0 / 1|

|151 – 280|G|32|3 / 4|1 / 2|

|281 – 500|H|50|5 / 6|1 / 2|

|501 – 1,200|J|80|7 / 8|2 / 3|

|1,201 – 3,200|L|200|10 / 11|3 / 4|

|3,201 – 10,000|M|315|14 / 15|5 / 6|

|10,001 – 35,000|N|500|21 / 22|7 / 8|

The Three Defect Tiers

• Critical Defects (AQL 0): Safety hazards or legal compliance violations (e.g., exposed wiring, missing FCC/CE marks). A single critical defect is an automatic batch failure.
• Major Defects (AQL 2.5): Flaws that ruin functionality or appearance, making a customer return inevitable (e.g., dead ports, deep scratches).
• Minor Defects (AQL 4.0): Small cosmetic flaws that don't affect performance (e.g., loose threads, wrinkled packaging).

FBA Pro-Tip: While AQL 2.5 is standard for general goods, you should tighten your limits to AQL 1.0 or 0.65 for electronics, baby products, or high-ticket items. One bad review wave can kill a listing.

4 Costly AQL Mistakes to Avoid

1. Accepting AQL 4.0 for Major Defects: Some factory-aligned inspectors try to use AQL 4.0 because it's faster. In a 200-unit sample, AQL 4.0 allows up to 14 major defects (a \~7% defect rate). That is way too high for Amazon FBA. Stick to AQL 2.5 or stricter.
2. Leaving AQL Out of Your Written Contract: Never rely on verbal quality agreements. Put your exact AQL metrics (e.g., General Level II, 0/2.5/4.0) directly into your binding Purchase Order (PO).
3. Combining Major and Minor Counts: Major flaws and minor cosmetics must be counted on completely separate mathematical tracks. Don't let an inspector bundle them together to make a bad report look average.
4. Treating Multiple SKUs as One Big Lot: If you have 1,500 units of SKU A and 1,500 units of SKU B, they are separate lots. You cannot pull a single sample pool across both. They must be sampled independently to catch issues isolated to specific production lines.