Flute size chart
Thickness is measured across the combined board (flute plus both liners). Values are typical: the exact figure varies by mill, liner weight and region, so confirm the real caliper with your board supplier before finalising a dieline.
| Flute | Thickness | Imperial | Flutes per foot | Typical use |
|---|---|---|---|---|
| A flute | ≈ 4.8 mm | 3/16 in | 33 ± 3 | Cushioning and stacking strength; less common today |
| C flute | ≈ 4.0 mm | 5/32 in | 39 ± 3 | The standard for shipping cartons and RSC boxes |
| B flute | ≈ 3.2 mm | 1/8 in | 47 ± 3 | Retail displays, die-cut boxes, canned-goods cases |
| E flute | ≈ 1.6 mm | 1/16 in | 90 ± 4 | Mailer boxes, subscription boxes, printed retail packs |
| F flute | ≈ 0.8 mm | 1/32 in | 125 ± 4 | Small retail boxes; a stronger folding-carton alternative |
More flutes per foot means smaller, tighter waves: a flatter, better printing surface and better crush resistance, but less cushioning and lower stacking strength than a larger flute with the same liners.
Single wall, double wall and triple wall
- Single wall: one flute between two liners. Covers most e-commerce and retail packaging.
- Double wall: two flutes and three liners, named by combination such as BC (about 6.5–7 mm) or EB (about 4.5–5 mm). Used for heavy, fragile or high-value goods and for stacking in storage.
- Triple wall: three flutes, used for bulk containers and industrial shipping.
Choosing a flute
Printed mailers and subscription boxes
E flute is the go-to for roll end tuck top mailers: crisp folds, a smooth surface for print, and enough stiffness to survive the post. Step up to B flute for heavier contents.
Shipping cartons
C flute is the standard for regular slotted containers. Use B flute for smaller, heavy items, and double wall for anything fragile, heavy or stacked high.
Retail boxes
F or E flute replaces folding carton board when a retail box needs more protection, for example for glass, electronics or premium gift sets.
Why flute thickness matters for the dieline
Corrugated board is thick enough that every fold changes the geometry. Inner flaps need extra clearance, roll-over walls must be inset, and slots must be wider than the board. A dieline drawn for 1.6 mm E flute will not fold properly in 4 mm C flute. Enter the real caliper and DielineKit adjusts these allowances; the caliper guide lists the allowances and a full point/mm conversion table.