Short answer
Box compression strength is the vertical load a box can carry before it collapses. It is predicted by BCT (box compression test), driven by the board's ECT (edge crush test) value, and reduced in real life by stacking time, humidity, pallet overhang and misaligned stacks.
The three numbers you will see on a spec
| Measure | What it tells you | Use it for |
|---|---|---|
| ECT (kN/m) | Edgewise crush resistance of the board | Comparing board grades for stacking |
| BCT (kg or N) | Load the finished box withstands | Predicting safe stack height |
| Bursting strength | Resistance to puncture | Sharp, dense or heavy contents |
Why real-world strength is lower
- Time: a box under constant load loses a significant share of its strength over weeks of storage.
- Humidity: damp warehouses soften fibres, and strength falls as moisture content rises.
- Overhang: any box hanging over the pallet edge loses the support of its strongest part, the corners.
- Misalignment: stacking corner-to-corner matters, because the corners carry most of the load.
- Perforations and hand holes: every cut-out reduces compression strength.
Designing for the stack, not just the product
The practical fix is usually simple: get the box footprint to fit the pallet properly, keep the stack square, and use the board grade that suits the stack height rather than the product weight alone. We will work the numbers with you as part of a free packaging review.
Frequently asked questions
- What is a good ECT value?
- It depends on stack height and weight. Light single wall cartons often sit around 23 to 32 ECT, while palletised double wall specs commonly run 44 ECT and above.
- Does printing reduce box strength?
- Flexo and digital print have minimal effect. Large die cuts, hand holes and perforations have a much bigger impact.
- Can you test my current box?
- We can review your pack, board specification and stack arrangement and recommend a grade that matches the load.
Think your packaging is bigger than it needs to be?
Send us your product dimensions and we’ll come back with a right-sized option. There is no minimum on stock lines, and bespoke corrugated runs can start from as little as one, but we will advise the most cost efficient run rate depending on size and board grade.
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