Corrugated Box Strength: ECT Ratings, Board Grades & What They Mean
Single-wall vs double-wall, B-flute vs C-flute, ECT 32 vs ECT 44. Understand box strength ratings and choose the right box for your product. Chengtop Packaging’s strength guide.
- Understand ECT (Edge Crush Test) ratings
- Compare flute types (A/B/C/E flute)
- Know single-wall vs double-wall
- Match box strength to product weight
- Learn stacking strength basics
- Avoid over-packing or under-packing
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Descripción
Too Weak = Broken Product. Too Strong = Wasted Money.
A box that’s too weak collapses in transit. A box that’s too strong costs more than it should. The right corrugated board grade protects your product without wasting money. Here’s how to read the ratings.
ECT Ratings
ECT = Edge Crush Test. Measures how much weight a box can handle on its edge.
|
ECT Rating
|
Board Type
|
Max Gross Weight
|
Best For
|
|
32 ECT
|
Single-wall
|
Up to 20 kg
|
Light products, retail
|
|
44 ECT
|
Single-wall
|
Up to 30 kg
|
Most shipping boxes
|
|
55 ECT
|
Double-wall
|
Up to 50 kg
|
Heavy products, stacking
|
|
67 ECT
|
Double-wall
|
Up to 70 kg
|
Industrial, export
|
For most e-commerce shipping, 32 ECT or 44 ECT single-wall is enough.
Flute Types
The flute is the wavy inner layer. Different flute profiles = different performance.
|
Flute
|
Height
|
Cushion
|
Stack Strength
|
Best For
|
|
A flute
|
5mm
|
Best cushion
|
Medium
|
Fragile products
|
|
B flute
|
3mm
|
Good cushion
|
Good
|
Retail, printing
|
|
C flute
|
4mm
|
Balanced
|
Balanced
|
General shipping (most popular)
|
|
E flute
|
1.5mm
|
Light cushion
|
Good (flat)
|
Retail folding cartons
|
|
F flute
|
1mm
|
Minimal
|
High (dense)
|
Premium retail packaging
|
Most common: C-flute for shipping boxes, B-flute for printed retail boxes.
Single-Wall vs Double-Wall
|
Single-Wall
|
Double-Wall
|
|
|
Layers
|
1 flute + 2 liners
|
2 flutes + 3 liners
|
|
Thickness
|
3–5mm
|
6–10mm
|
|
Weight
|
Light
|
Medium-Heavy
|
|
Stack strength
|
Up to 6 layers
|
Up to 10 layers
|
|
Cost
|
Lower
|
Higher
|
|
Best for
|
Most shipping
|
Heavy products, export
|
Match Strength to Product Weight
|
Product Weight
|
Recommended Box
|
|
Under 5 kg
|
32 ECT single-wall, B or C flute
|
|
5–15 kg
|
32–44 ECT single-wall, C flute
|
|
15–30 kg
|
44 ECT single-wall or 55 ECT double-wall
|
|
30–50 kg
|
55 ECT double-wall
|
|
Over 50 kg
|
67 ECT double-wall
|
Stacking Strength
How high can you stack?
|
Board Grade
|
Stack Height (per box)
|
|
32 ECT
|
4–6 layers
|
|
44 ECT
|
6–8 layers
|
|
55 ECT double-wall
|
8–10 layers
|
|
67 ECT double-wall
|
10+ layers
|
Remember: stack strength drops by 30% if boxes are stored in humid conditions.
Common Strength Mistakes
- Box too weak for product weight — Box bulges or breaks
- Box too strong for light product — Wastes money on unnecessary strength
- Wrong flute type — E-flute for shipping (not enough cushion)
- No consideration for humidity — Box strength drops 30% in damp storage
- Over-stacking — Bottom boxes crush under weight
- Ignoring product fragility — Heavy box doesn’t help if product is fragile (need inserts too)
How We Help
- We recommend ECT rating based on your product weight
- We supply single-wall and double-wall boxes
- We offer all flute types (B/C/E)
- We test box strength before bulk production
- We advise on stacking height based on your warehouse
Need Help Choosing the Right Box Strength?
Tell us your product weight and how many layers you stack — we’ll recommend the right board grade.
Correo electrónico: chengtop888@outlook.com
WhatsApp / Teléfono: +86 15272060604
