Understanding Box Strength: ECT vs Mullen Test Explained
Two Ways to Rate Board
Corrugated boxes are commonly rated by one of two tests. The rating usually appears on the box maker certificate stamped on a flap.
Edge Crush Test (ECT)
ECT measures how much force a strip of board can take on its edge before it crushes, in pounds per linear inch. It relates directly to stacking strength, which is why it has become the most common rating for shipping boxes. Common single wall ratings are 32 ECT and 44 ECT.
Mullen Burst Test
The Mullen test measures the pressure needed to burst through the face of the board, in pounds per square inch. It relates to puncture resistance and rough handling. Common single wall ratings are 200# and 275# test.
Which Should You Use?
If boxes will be stacked on pallets or in storage, ECT is the more useful number. If boxes face rough handling and puncture risks, burst strength matters too. Either way, size, moisture, and condition affect real-world performance, so treat the rating as a guide.
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