Edge Crush Test Explained

What ECT ratings mean, how they predict stacking strength, how ECT differs from burst strength, and how to choose the right rating for your supply chain.

The Edge Crush Test, usually shortened to ECT, measures how much force a strip of corrugated board can withstand when loaded on its edge. The result is expressed in kilonewtons per metre (kN/m) and is the best single predictor of how well a box will hold up in a stacked pallet load.

What the test involves

A small sample of board is cut into a strip and placed vertically between two platens. Force is applied downwards until the flute structure collapses. The maximum force divided by the sample length gives the ECT value. Higher values mean better stacking strength.

Common ECT ratings and what they suit

• 32 ECT: light retail and postal boxes, single wall, low stack heights.
• 44 ECT: standard shipping boxes, single wall, moderate pallet loads.
• 48 ECT: heavier single wall or lighter double wall applications.
• 51 ECT and above: heavy or stacked loads, double wall BC, export or multi-handling.

These are starting points. The actual box performance also depends on dimensions, flute type, moisture and how evenly the load is distributed.

ECT versus burst strength

ECT tells you how much weight a box can carry from above. Burst strength tells you how much pressure the wall can take before it tears. ECT is the right guide for stacking and warehousing. Burst matters more for rough handling, point loads and impacts during transit.

Why this matters for your costs

Over specifying ECT wastes money and adds weight. Under specifying leads to crushed pallets, damaged goods and returns. The cheapest box is the one that is just strong enough for the real journey it takes.

Tell us the weight of your product, the stack height and the journey length and we will recommend an ECT rating, make a sample and let you test it before you commit to a full production run.