Corrugated boxes come in several flute types, and the flute you choose directly affects cushioning, stacking strength, print quality, and box thickness. This guide explains the four most common flute profiles so you can pick the right one for your product.
What is a flute?
A flute is the wavy, arched layer of paper sandwiched between the flat liners of corrugated board. Those arches act like columns, giving the board its strength and cushioning. Flutes are graded by letter based on their height and the number of flutes per foot.
A-Flute
A-flute is the thickest common profile at roughly 3/16 inch (about 5 mm). It offers the best cushioning and stacking strength, making it ideal for fragile or heavy products that need maximum protection in transit.
B-Flute
B-flute is about 1/8 inch (3 mm) thick with more flutes per foot. It provides a flatter, smoother surface that prints well, so it is common for retail packaging, canned goods, and die-cut boxes.
C-Flute
C-flute sits between A and B at roughly 11/64 inch (4 mm). It is the most widely used flute for shipping boxes because it balances cushioning, stacking strength, and printability—a true all-rounder.
E-Flute
E-flute is much thinner at about 1/16 inch (1.5 mm). Its fine profile delivers an excellent print surface, which is why it is the go-to choice for mailer boxes and retail-ready packaging where branding matters.
Comparison at a glance
| Flute | Thickness | Best for |
|---|---|---|
| A-Flute | ~3/16” (5 mm) | Heavy or fragile items, maximum cushioning |
| B-Flute | ~1/8” (3 mm) | Retail boxes, canned goods, strong print surface |
| C-Flute | ~11/64” (4 mm) | General shipping boxes, balanced performance |
| E-Flute | ~1/16” (1.5 mm) | Mailer boxes, retail-ready, premium print |
How to choose
For most e-commerce shipping, C-flute single-wall is the safe default. Choose E-flute for branded mailer boxes, B-flute when print quality matters on retail shelves, and A-flute or double-wall (such as BC) for heavy or fragile freight.
Need help deciding? Get a free quote and our specialists will recommend the right board grade for your product.