Why Strength Ratings Matter
Box strength ratings ensure your packaging can handle stacking, handling, and shipping stresses without failure. Choosing the wrong strength leads to product damage.
- •Protects products during stacking in warehouses
- •Prevents crushing during carrier handling
- •Ensures survival of shipping conditions
- •Proper strength selection reduces damage claims
ECT (Edge Crush Test) Ratings
ECT measures the box's ability to resist crushing forces. It's the modern standard for rating corrugated box strength.
- •ECT measures pounds per linear inch of edge crush resistance
- •32 ECT: Standard strength for items up to 65 lbs
- •44 ECT: Medium strength for items up to 80 lbs
- •48 ECT: High strength for items up to 95 lbs
- •Higher ECT ratings available for heavy applications
Mullen (Burst) Test
The Mullen test measures the pressure required to puncture the corrugated board. It was the traditional standard before ECT became common.
- •Measures pounds per square inch of burst resistance
- •200# test: Light-duty, basic shipping
- •275# test: Standard shipping applications
- •350# test: Heavy-duty applications
- •ECT and Mullen are not directly interchangeable
Weight Capacity Guidelines
Box weight capacity depends on ECT rating, box size, and stacking conditions. Larger boxes require higher ECT ratings for the same weight.
- •32 ECT: Up to 65 lbs in typical sizes
- •44 ECT: Up to 80 lbs in typical sizes
- •48 ECT: Up to 95 lbs in typical sizes
- •Larger boxes reduce effective weight capacity
- •Environmental conditions affect performance
Stacking Strength Considerations
Warehouse stacking multiplies the forces on bottom boxes. Consider your stacking requirements when selecting box strength.
- •Bottom boxes bear weight of entire stack
- •10-high stack = 10x the weight on bottom box
- •Humidity reduces stacking strength up to 50%
- •Add safety factor of 3x for real-world conditions
Selecting the Right Strength
Match box strength to your specific application considering product weight, fragility, stacking requirements, and shipping conditions.
- •Calculate actual weight plus cushioning materials
- •Consider maximum stacking height in warehouse
- •Account for humidity and climate conditions
- •Add safety margin for rough handling