Choosing a Corrugated Box Grade - Which One Fits?
The right corrugated grade decides whether a parcel survives shipping intact. This guide explains flute type and profile, the key values bursting strength and Edge Crush Test (ECT), and how to select by weight and transport route.
View shipping boxesSingle or double wall - which flute type when?
Corrugated board is classified by the number of fluted layers and by the flute profile. Single-wall board has one fluted layer between two liners, double-wall has two flutes between three liners. A taller flute cushions better, a finer flute gives a smoother surface and better printability.
Profiles are named by letters: B-flute (about 2.5 mm) is flat and print-friendly, C-flute (about 3.6 mm) adds cushioning, E-flute (about 1.5 mm) is a fine micro-flute for folding cartons. Double-wall combinations such as BC or EB merge the strengths of two profiles.
Bursting strength or ECT - what shows quality?
Two values describe the mechanical quality of corrugated board. Bursting strength (BST, in kPa) measures the pressure a face can take before it ruptures - it describes resistance to puncture and point loads. The Edge Crush Test ECT (in kN/m) measures the crush force of the upright edge and correlates directly with stacking strength.
For stacked goods in the warehouse or on a pallet, ECT is the more meaningful value because load is carried vertically through the edges. For bulky or sharp contents that push from inside, bursting strength gains importance. Both are tested per ISO 3035 (burst) and ISO 3037 (ECT).
- Bursting strength (BST): resistance to puncture, good for heavy single items.
- ECT: edge crush resistance, decisive for pallet stacks.
- Basis weight: heavier paper generally raises both values.
- Humidity: high moisture lowers ECT and burst strength markedly.
How do I select by weight and shipping route?
The right grade follows from product weight, fragility and transport route. As a rough guide, single-wall B- or C-flute covers up to about 20 kg, while double-wall BC carries much more and better survives the rough handling of a parcel network. For palletised, stacked shipping the ECT of the whole packaging column matters.
Frequently asked questions
What do BC or EB mean on corrugated board?
The letters stand for the combined flute profiles of a double-wall board. BC merges B- and C-flute for high strength, EB combines the fine E-flute with the B-flute for a smooth surface and good cushioning.
Is bursting strength or ECT more important?
For stacked goods on pallets the ECT (edge crush resistance) is decisive because it describes stacking strength. For shock-prone single parcels the bursting strength is more meaningful.
Which corrugated grade for heavy shipments over 20 kg?
For heavy or fragile goods use double-wall board, usually in BC quality. It offers high burst and edge crush values and survives multiple handling better than single-wall board.
Does corrugated board lose strength when damp?
Yes, high humidity lowers ECT and bursting strength markedly because the paper absorbs water. In humid conditions or chilled transport, choose a higher grade or a coated board.
Looking for the right corrugated grade?
We supply shipping boxes in single- and double-wall quality with tested ECT and burst values - matched to weight and shipping route.
Tested values
ECT and bursting strength per ISO 3035 and 3037.
All flute types
Single- and double-wall from E to BC available.
Ship-proof
Grades matched to weight and transport route.
Expert advice
Our team helps you choose the right board grade.