What Is Corrugation?
Corrugation is the wavy, fluted layer of paper sandwiched between flat liners to make corrugated board. The arched flutes act like columns, giving the board its stacking strength, stiffness, and cushioning while keeping it light.
In more detail
Corrugation is what turns flat paper into a structural packaging material. A sheet of paper (the medium) is passed through heated, geared rollers that press it into a continuous series of arches called flutes. Those flutes are then glued between one or more flat sheets (liners) to form corrugated board.
The reason it works is geometry. Each arch behaves like a tiny column and a tiny spring at once: it resists crushing from above (stacking strength) and absorbs shock from the sides (cushioning). That is why a corrugated box, made of nothing but paper and air, can protect heavy or fragile goods through a rough supply chain.
The size and shape of the flute, its profile, changes the board's character. Bigger flutes (A, C) give more cushioning and stacking strength; smaller flutes (E, F) give a smoother surface for fine printing. Combining two flutes makes double-wall (5-ply) board for heavier loads.
Key points
- The flute is the wavy layer; liners are the flat sheets glued to it
- Flutes act as columns (strength) and springs (cushioning)
- Profiles A–F trade cushioning and strength against print smoothness
- More flute layers = stronger board (3-ply single wall, 5-ply double wall)
Common questions
What is the purpose of corrugation in a box?
The corrugated (fluted) layer gives the board its strength and cushioning without adding much weight. The arches resist crushing when boxes are stacked and absorb shocks during handling and transit, which is what protects the product inside.
What are the different flute sizes?
Common profiles are A (~4.7 mm, most cushioning), C (~3.6 mm, export standard), B (~2.5 mm, all-round), E (~1.5 mm, retail print), and F (~0.8 mm, premium micro-flute). Larger flutes give more strength and cushioning; smaller flutes give a finer print surface.
Related terms
Where it's used
Written by LeRoy Print Packs, a printing and packaging manufacturer making cartons, corrugated boxes and labels in-house. Get a quote