Flute profiles (A, B, C, E, F, N)

The canonical reference for corrugated flute dimensions. A through N: what each profile is, how thick it is, how many flutes per metre, and what it's actually used for.

Corrugated board is not a single product — the wave geometry at its core varies systematically across six main profiles, each making different tradeoffs between board thickness, cushioning, print surface quality, and material efficiency. Knowing which flute profile is specified (or which is appropriate for a given application) is fundamental to box design.

The flute designation (A, B, C, E, F, N) is historical rather than alphabetically systematic. A-flute was commercialised first; B came second; C filled a middle position. E was developed as a thinner "fine" flute; F, N, and G as even thinner microflutes for premium retail. The letters do not indicate a ranking by quality.

Dimensions at a glance

| Flute | Flutes per metre | Board thickness (mm) | Best applications | |-------|-----------------|---------------------|-------------------| | A | ~110 | 4.7–4.8 | Heavy shipping, cushioning, industrial transit | | B | ~150 | 3.0–3.2 | Canned goods, small shipping boxes, die-cut RSC | | C | ~125–130 | 3.7–4.0 | General shipping, outer shipper cases | | E | ~290–295 | 1.5–1.6 | Retail display, pizza boxes, high-print quality | | F | ~390–420 | 0.75–0.8 | Cosmetics, premium consumer goods, tight tolerances | | N | ~540–560 | 0.45–0.55 | Jewellery, luxury, replace folding carton |

Values are approximate and vary by corrugator roll specification. Manufacturers may run slightly different roll pitches; always verify with your corrugated converter's specific die library.

A-flute

A-flute is the tallest and most open of the standard profiles. At ~4.8 mm board thickness with ~110 flutes per metre, it delivers excellent cushioning and high stacking strength per unit of liner weight — the tall arches distribute load efficiently.

The tradeoff is material usage: A-flute consumes the most corrugating medium per square metre of finished board (roughly 1.45× the area of the flat liner), and the thick board is harder to die-cut and score cleanly. A-flute is the right choice when the primary concern is product protection during rough transit — heavy equipment, fragile glassware, fruit and vegetable export cartons that will stack 8–10 high in a cold-chain container.

B-flute

B-flute was the second profile standardised and remains the most versatile for consumer goods. At ~3.2 mm thickness with ~150 flutes per metre, the shorter, more frequent waves produce a stiffer flat crush resistance than A-flute and a better printing surface (flatter, less telegraphing of the flute structure through the liner).

Canned goods, bottled beverages, and dairy multipacks are the classic B-flute application: the boxes need good stacking strength (they're palletised high) and reasonable print quality (they sit on retail shelves), but weight savings are valued, and heavy cushioning is not required because the contents are robust. B-flute boxes also fold and score more predictably than A-flute, which matters for high-speed form-fill-seal packaging lines.

C-flute

C-flute occupies the middle ground between A and B and has become the dominant profile for general export and shipping containers. At ~4.0 mm thickness with ~130 flutes per metre, it matches A-flute closely in stacking strength while improving slightly on print surface quality.

The practical reality is that C-flute has absorbed a huge share of the A-flute market simply by being better balanced. If you are specifying a general-purpose outer shipping carton with no unusual cushioning or print requirements, C-flute on a 125/125/125 g/m² liner-medium-liner spec is where to start.

The corrugating medium used in C-flute is the same OCC-based fluting as other profiles; the distinction is purely in the roll geometry on the corrugator.

E-flute

E-flute is where corrugated stops being purely structural and starts competing with folding carton. At ~1.6 mm thickness and ~290 flutes per metre, E-flute board is thin enough to be scored and folded on machinery originally designed for solid board — folding carton type setters and die-cutters.

The much tighter wave pitch means less telegraphing of flute structure through the printing surface, enabling offset litho print quality on the outside liner. E-flute is standard for pizza boxes, small retail display units, toy boxes, and any application where the box is both the shipping container and the retail package — a segment that has grown substantially with direct-to-consumer e-commerce.

E-flute uses significantly less medium per square metre than C-flute, and the thinner board nests more compactly for storage. Against that: lower stacking strength per unit area (shorter arches), and the board is more susceptible to moisture weakening.

F-flute

F-flute (sometimes called FF or fine flute, ~0.8 mm) pushes further into folding carton territory. At this scale, the corrugated structure provides glue-able rigidity and some cushioning but not meaningful stacking strength comparable to coarser flutes. F-flute is used for cosmetics packaging, small electronics accessories, and premium food retail where dimensional accuracy, high print quality, and lightweight construction are the priorities.

At 0.8 mm, F-flute board competes directly with 400–600 g/m² solid fibreboard on weight and dimensional stability, while offering better cushion per gram and (for non-coated designs) a more sustainable credential by avoiding clay coatings.

N-flute

N-flute (~0.5 mm, ~550 flutes per metre) is the finest commercially available corrugated profile. The board is barely distinguishable from solid board to the touch; the corrugation is visible only under a loupe. N-flute is used for jewellery boxes, luxury cosmetics, and high-end retail packaging where the brand positioning demands solid-board aesthetics and folding-carton tolerances, but the designer wants the structural integrity benefit of a corrugated core.

N-flute production requires tighter tension and temperature control on the corrugator than coarser profiles; not all converters can run it at acceptable yields.

Combining flutes: double-wall

Single-wall board uses one flute between two liners. Double-wall (DW) stacks two flute layers, typically with a middle liner between them. Common DW combinations are BC (B-flute plus C-flute), EB (E plus B), and BB (double B). Double-wall board achieves stacking strengths approaching heavy solid fibreboard at lower basis weight.

WPI editorial note: The flute profile is only half the equation. A C-flute box with 100 g/m² recycled testliner will fail under a stack load that a B-flute box with 175 g/m² virgin kraft liner will carry comfortably. Always specify flute profile and liner/medium grammage together — one without the other is not a specification.