What Is a Corrugated Box? Flutes, Wall Types, and Uses
A corrugated box is the strong, fluted box you use for shipping. Most people call it cardboard, but that is not quite right. A corrugated box has a wavy inner layer that makes it tough. This guide explains what a corrugated box is, how it differs from plain cardboard, the wall and flute types, and when to use one. It is written in plain terms for US brands.
Quick answer: corrugated in four points
- What: a wavy fluted layer glued between two flat liners.
- Why: the waves add strength and cushioning.
- Best for: shipping, heavy items, and mailers.
- Not the same as: plain cardboard, which is a single sheet.
What is a corrugated box?
A corrugated box has three layers. There are two flat outer liners. Between them sits a wavy layer called the flute. The waves act like little arches, so the box resists crushing and cushions the product. That is why almost all shipping boxes are corrugated. See our corrugated boxes.
Corrugated vs cardboard: what is the difference?
People mix these up all the time. Plain cardboard is a single thick sheet, like a cereal box or a folding cardboard box. Corrugated has the wavy inner layer, so it is much stronger. If a box needs to survive shipping, you want corrugated.
Single, double, and triple wall
Wall type means how many fluted layers the board has.
| Wall type | Strength | Best for |
|---|---|---|
| Single wall | Strong | Most shipping and retail boxes |
| Double wall | Very strong | Heavy or stackable products |
| Triple wall | Heavy-duty | Industrial and very heavy loads |
What are flute grades?
Flutes are the waves inside the board. They come in sizes, graded by letter.
| Flute | Thickness | Best for |
|---|---|---|
| A-flute | Thickest | Cushioning fragile or heavy items |
| B-flute | Thin | Retail boxes with good print |
| C-flute | Medium | The most common shipping boxes |
| E-flute | Very thin | Printed mailers and small retail boxes |
| F-flute | Thinnest | Small, premium retail packaging |
For a wider look at stocks, see our box material guide.
When should I use a corrugated box?
Reach for corrugated when strength matters:
- Shipping boxes and heavy products that must survive the carrier.
- Mailer boxes in E-flute, which print sharp and still protect.
- Retail-ready and stackable boxes that hold their shape on a shelf.
How much do corrugated boxes cost?
Cost depends on size, wall type, print, and quantity. Double wall costs more than single wall. Larger orders cost less per box. Runs start at 100 units with no setup or die fees. For a full breakdown, see how much custom boxes cost.
Frequently asked questions
What is a corrugated box?
A corrugated box is made of three layers: a wavy fluted layer glued between two flat liners. The waves add strength and cushioning, which is why corrugated boxes are used for shipping.
Is corrugated the same as cardboard?
No. People say cardboard, but they often mean corrugated. Plain cardboard is a single thick sheet, like a cereal box. Corrugated has a wavy inner layer between two liners, so it is much stronger.
What is the difference between single and double wall?
Single wall has one fluted layer and suits most shipping. Double wall has two fluted layers for heavy or stackable items. Triple wall is for very heavy, industrial loads.
What are flute grades?
Flutes are the waves inside the board, graded by size: A and C are thicker for cushioning, B is good for retail print, and E and F are thin for small boxes with sharp print.
When should I use a corrugated box?
Use corrugated for shipping, heavy products, and anything that needs to survive the carrier. E-flute corrugated also makes a great printed mailer or retail box.
Is there a minimum order for corrugated boxes?
Runs start at 100 units with no setup or die fees, so you can order custom printed corrugated boxes without a large minimum.
Need boxes that ship safe? Custom Box Printing makes custom printed corrugated boxes for US brands, in single and double wall, with free design help, a free sample, and free US shipping, starting at 100 units. Request a free quote to get started.
