Testing Packaging Stacking – How Much Can Be Stacked?

 Stacking strength testing is essential to determine how many packages can be safely stacked during storage and transportation without causing damage. The stacking ability depends on box material, construction, weight, and environmental conditions.

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1. Stacking Strength Testing Standards

Several international standards guide packaging stacking tests:

• ASTM D642 – Standard test method for determining compressive resistance of shipping containers.
  
  
  
• ISTA 3E – Defines stacking tests for unitized loads in distribution environments.
• ISO 2234 – Stacking performance test for transport packages.

These standards ensure packaging can withstand warehouse storage and transit conditions.

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2. How to Determine Stacking Strength?

The maximum stack height depends on Box Compression Test (BCT) values and real-

world handling conditions.

A. Box Compression Test (BCT) Formula

The stacking strength of a box can be estimated using McKee’s formula:

$$BCT = 5.87 \times ECT \times \sqrt{(P \times T)}$$

Where:

• BCT = Box Compression Strength (lbs or kg)
• ECT = Edge Crush Test value (lbs/in or kN/m)
• P = Perimeter of the box (inches or cm)
• T = Thickness of the corrugated board (inches or mm)

Example:
If a corrugated box has an ECT of 32 lbs/in, with a perimeter of 60 inches and a board thickness of 4 mm, the BCT can be calculated.

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B. Safe Stacking Load Calculation

The maximum stacking load is determined by applying a safety factor based on storage duration and environmental conditions:

$$Stacking Load = \frac{BCT}{Safety Factor}$$

Storage Condition	Recommended Safety Factor
Warehouse (Short Term)	3
Long-Term Storage	5
High Humidity	6

✅ Example Calculation:
If a box has a BCT of 1,000 kg, and it is stored long-term in a warehouse, the safe stacking load would be:

$$\frac{1000}{5} = 200 \text{ kg per box}$$

So, if each box weighs 20 kg, the stack height can be:

$$\frac{200}{20} = 10 \text{ boxes}$$

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3. Factors Affecting Stacking Strength

Several conditions impact the stacking ability:

A. Corrugated Board Quality

• Single-wall board: Lower stacking strength (ECT 26–32 lbs/in).
• Double-wall board: Medium strength (ECT 42–48 lbs/in).
• Triple-wall board: High stacking strength (ECT 60+ lbs/in).

B. Box Orientation & Load Distribution

• Stacking vertically aligns edges for maximum strength.
• Interlocked stacking (brick stacking) reduces stability.
• Load spreaders (pallet boards) help distribute weight evenly.

C. Environmental Conditions

• Humidity & moisture weaken corrugated board strength.
• Temperature fluctuations impact box rigidity.

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4. Real-World Stacking Guidelines

• For e-commerce & retail packaging: 4–6 boxes per stack.
• For warehouse pallet stacking: 8–12 boxes per stack with proper support.
• For export shipments: Use pallet wrap & corner supports to maintain stability.

✅ Tip: Always test actual conditions using compression and stacking tests to validate safe stacking limits.

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Conclusion

To determine how much can be stacked, perform a Box Compression Test (BCT), apply a safety factor, and consider storage conditions. Use high-quality corrugated materials, proper stacking techniques, and environmental controls to prevent package failures.