Corrugated Board Grades Explained: ECT, Flutes, and Single vs. Double Wall
Corrugated is not just ‘cardboard.’ The board grade determines whether your product arrives intact and how much you pay to get it there. A little literacy here saves money in both directions — no shipping a fragile candle in flimsy board, and no armor-plating a t-shirt.
Flute profiles
| Flute | Thickness | Best for |
|---|---|---|
| E-flute | ~1.5 mm | Retail, mailers, crisp print |
| B-flute | ~3 mm | General shipping, cases |
| C-flute | ~4 mm | Shipping with cushioning |
| BC double-wall | ~7 mm | Heavy, fragile, freight |
What ECT means
Edge Crush Test (ECT) rates stacking strength — how much weight a column of boxes can bear before crushing. 32 ECT is the common single-wall standard; 44 and up move you into double-wall territory for heavy or stacked freight. Spec to your product weight and how high pallets get stacked, not to a gut feeling.
Single vs. double wall
Single-wall covers the vast majority of e-commerce. Double-wall is for genuine weight, glass, or long freight journeys with rough handling. Paying for double-wall on a light product is a common, quiet overspend.
Spec board to product weight and stack height. 32 ECT single-wall handles most DTC; reserve double-wall for heavy, fragile, or freight.
Choosing for your order
Tell us what is going in the box and how it ships. We will recommend the lightest board grade that protects it — and quote it.
Ready to order? Request a free mockup and bulk quote — or read more on our blog and about page.
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