If your business activities often need to ship a variety of products, then the choice of packaging is definitely a problem you can’t escape. And among the different packaging box, you’ll find corrugated boxes used in various ways throughout the packaging industry. Corrugated boxes often worked as packaging for easy shipping. The widespread use of corrugated boxes is the result of many factors, not just because of its low cost but also because of the structure of the corrugated paper.
This blog aims to explain and clarify everything you need to know about corrugated paper and flute paper. Keep reading to learn about the different types of corrugated cardboard and their uses.
1. What is flute paper?
Flute paper is the wavy layer of paper that’s sandwiched between two flat sheets of paper in a corrugated box. It gives the box its strength and cushioning, which helps protect products during shipping. The wavy structure of the flute paper allows the box to absorb impact and pressure without crushing.
In short:
Flute paper = the wavy, middle layer inside a corrugated box that provides strength.
2. What is corrugated paper?
Corrugated paper (or corrugated board) is the finished material used to make boxes. It consists of three layers:
- Two flat layers of paper (linerboards)
- One wavy layer of flute paper between them
When these layers are glued together, it forms the strong, protective material that’s used for shipping boxes, packaging, and more. The combination of the flat layers and the flute paper is what makes corrugated paper both strong and lightweight.
In short:
Corrugated paper = three layers — two flat layers with a wavy flute layer in the middle.
Corrugated paper = flat sheet + flute paper + flat sheet
3. Different flute sizes
Flute sizes are simply the different wave patterns inside corrugated cardboard.
The size of the flute affects how thick, strong, and printable the board is.
General rule (the true version):
Bigger waves (large flutes) = better cushioning and good stacking strength
Smaller waves (small flutes) = better printing, cleaner edges, easier folding, and good crush strength
In a nut shellDifferent, flute sizes give corrugated boxes different strengths and benefits.
Larger flutes provide better cushioning and stacking strength, while smaller flutes offer better printing quality and foldability. Each flute type has its own purpose in packaging.
A-Flute
- Thickness: 1/4 inch
- Best For: Fragile products that need maximum protection
- Key Benefits:
- Excellent cushioning due to its thickness
- Great short-column compression resistance (resists crushing when stacked)
- High stiffness, making it ideal for products that need extra protection during shipping
Why it’s used:
The A-flute is often the best choice for fragile items (like electronics, glassware, etc.) because it offers a cushioned layer that absorbs shocks and prevents damage during transport.
B-Flute
- Thickness: 1/8 inch
- Best For: High-quality printing and compact packaging
- Key Benefits:
- More grooves per foot compared to A-flute, which creates a flatter, smoother surface for printing
- Better puncture and crush resistance than A-flute, especially for lightweight products
- Space-efficient, takes up less room in storage
- Suitable for high-speed packaging lines, as it folds easily and handles automated processes well
Why it’s used:
B-flute is commonly used in high-speed packaging, mailers, and inner packaging like dividers or partitions. It’s also popular for certain retail boxes, like beer and wine cases, due to its good print surface and durability.
C-Flute
- Thickness: 3/16 inch
- Best For: Shipping and stacking strength
- Key Benefits:
- Provides a balance of cushioning and strength
- Works well for light to medium weight products
- Often used for shipping boxes because of its good stacking strength
Why it’s used:
The C-flute is ideal for standard shipping boxes, providing a good mix of strength and cushioning for medium-weight items. It’s one of the most common flute types for shipping.
E-Flute
- Thickness: 1/16 inch
- Best For: Small packaging, high-quality printing
- Key Benefits:
- Very thin but still strong enough to be used for folding cartons
- Provides an excellent smooth surface for printing, making it ideal for retail boxes with intricate graphics
Why it’s used:
The E-flute is great for retail packaging, particularly when you need a smooth, printable surface. It’s commonly used in packaging like cosmetic boxes, gift boxes, and high-end retail packaging where print quality is important.
F-Flute
- Thickness: Similar to E-flute, slightly thinner
- Best For: Small retail packaging
- Key Benefits:
- Comparable to E-flute in terms of thickness, but typically used for smaller packaging needs
- Often interchangeable with E-flute for compact retail boxes
Why it’s used:
The F-flute is designed for small, lightweight retail packaging. It’s strong enough for retail use but compact enough for smaller boxes that need to be printed and displayed in stores.
4. The material used for corrugated paper
Generally speaking, the paper used for corrugated board is mainly kraft paper. Kraft paper is made from coniferous trees, and due to the “virgin” fibers, it is the strongest type of paper and the easiest to print on. In addition, the paper types that can be used for the outer liner and the flute when making corrugated board also include the following type:
| CHIP (C): | Waste based liners |
| FULLY BLEACHED WHITE (BW) | Fully bleached Kraft liner |
| WHITE TOP (WT) | White coated recycled liner |
| MOTTLED KRAFT (MK) | Mottled white Kraft |
| OYSTER (OY) | Mottled test liner |
| SEMI CHEM (SC) | Virgin fibers using neutral sulphite semi-chemical process |
| WASTE BASED (WB) | 100% recycled fibers |
5. Types of Corrugated Cardboard
#1. Single-Wall Corrugated Board
Structure: Liner → Flute → Liner
Single-wall is the most common type of corrugated board. It’s widely used for e-commerce boxes, mailers, and lightweight shipping cartons. Single-wall offers a good balance of strength, protection, and cost-efficiency, making it the standard choice for everyday packaging needs.
#2. Double-Wall Corrugated Board
Structure: Liner → Flute → Liner → Flute → Liner
Double-wall corrugated board adds an extra layer of flute and liner, providing greater strength and durability. It’s ideal for heavier products, industrial packaging, and larger cartons. Its design also makes it suitable for products that require extra stacking strength during shipping.
#3. Triple-Wall Corrugated Board
Structure: Liner → Flute → Liner → Flute → Liner → Flute → Liner
Triple-wall corrugated board is the heaviest and strongest option, often used as a replacement for wooden crates. It’s perfect for heavy machinery, chemicals, or any products that need maximum protection during transport. With three layers of fluting and four liners, it combines extreme strength with durability, making it the go-to solution for high-risk shipments.
Why Flute Type and Board Construction Matter?
The combination of liner sheets and flute layers determines a box’s strength, cushioning, and printability. By choosing the right construction—single, double, or triple wall—you can match packaging to your product’s weight, fragility, and shipping conditions.
Pro Tip:
For standard consumer goods, single-wall is usually sufficient. For heavier or fragile items, double-wall or triple-wall ensures the product arrives safely while reducing the risk of crushing or damage.
FAQ
Q1: What is the difference between fluting paper and kraft paper?
Fluting paper: wavy middle layer, flexible, absorbs shocks
Kraft paper: flat outer layer, strong, provides box strength and printable surface
Q2: What is corrugated paper used for?
Corrugated paper is used to make shipping boxes, mailers, retail boxes, and industrial cartons. It’s lightweight, strong, and protective.
