Paperboard grades and board thickness for boxes

The board you choose decides how a box looks, feels, protects and costs. Too thin and the box crushes, bows or feels cheap. Too thick and you pay more for material, freight and storage than you need to. This guide explains the main types of board used in packaging, how thickness and weight are measured, and how to choose the right board for folding cartons, mailers and rigid boxes.

Three families of packaging board

Most custom boxes use one of three families of board:

1. Paperboard (folding boxboard) for retail cartons such as tuck end boxes and sleeves.
2. Corrugated board for mailers, shipping boxes and displays.
3. Rigid greyboard for premium rigid boxes, wrapped in printed paper.

Each is measured differently and suits different jobs.

Paperboard grades

Paperboard is a thick, stiff paper used for folding cartons. There are several common grades.

SBS (solid bleached sulfate)

Made from bleached virgin fibre, white throughout. SBS has a smooth surface that prints very well and gives bright, accurate colours. It is often used for cosmetics, pharmaceuticals, premium food and luxury retail.

Pros: excellent print quality, clean white edges, good for fine finishes. Cons: typically more expensive, virgin fibre.

FBB (folding boxboard)

A multi-layer board, usually with bleached outer layers and a mechanical pulp middle. It is lighter for a given stiffness than SBS and widely used for food, healthcare and consumer goods.

Pros: good stiffness for its weight, good print surface. Cons: the middle layer may be visible at cut edges.

CRB (coated recycled board)

Made from recycled fibre, with a coated white top surface for printing. Often grey on the reverse. Common for cereal boxes, household goods and many everyday cartons.

Pros: recycled content, often lower cost. Cons: less smooth than SBS, grey reverse, may not suit all food-contact uses without barriers.

Kraft board

Made from unbleached fibre, with a natural brown colour. Strong and often chosen for a natural or rustic look.

Pros: strong, natural appearance. Cons: colours print darker and duller; white ink may be needed.

Measuring paperboard

Paperboard is measured in two main ways:

• Weight (gsm): grams per square metre. Common folding carton weights range from around 250 gsm to 450 gsm.
• Thickness (points or microns): in the US, thickness is often given in points, where one point is one thousandth of an inch (0.001 in). Common carton boards range from around 14 pt to 24 pt.

Gsm and thickness are related but not interchangeable. Different grades have different densities, so two boards of the same gsm can have different thicknesses and stiffness.

Choosing paperboard

• Small, light products such as lip balms or sachets: lighter boards, around 250 to 300 gsm, are often enough.
• Most retail cartons for cosmetics, supplements and food: around 300 to 400 gsm.
• Larger or heavier products, or cartons that need to feel premium: heavier boards, or a switch to corrugated or rigid.
• Very small cartons: heavy board can be hard to fold neatly on small panels, so the lightest suitable board often gives a cleaner result.

Corrugated board

Corrugated board is made of a wavy fluted layer glued between flat liners. The flutes give strength and cushioning while keeping weight down.

Flute sizes

Common flutes, from thinnest to thickest:

| Flute | Approx. thickness | Typical uses | |---|---|---| | F-flute | about 0.8 mm | Small retail boxes, premium mailers | | E-flute | about 1.5 mm | Mailer boxes, retail packaging, displays | | B-flute | about 3 mm | Shipping boxes, heavier mailers, displays | | C-flute | about 4 mm | Shipping cartons, heavier products | | BC double wall | about 6 to 7 mm | Heavy or fragile shipments |

Exact thicknesses vary by manufacturer.

Liners

Liners can be kraft (brown) or white, and coated or uncoated. For high-quality print, many mailers use a litho-laminated construction: printed paper laminated onto the corrugated board.

Strength ratings

Corrugated board strength is often described by edge crush test (ECT) values or burst strength. For shipping boxes, ask your manufacturer to recommend a grade based on product weight, stacking and shipping method.

Choosing corrugated board

• E-flute is the default for most e-commerce mailers: strong enough for many products, with a smooth surface for printing.
• B-flute suits heavier products and shipping boxes.
• Double wall suits heavy or fragile items or long-distance shipping.

Rigid greyboard

Rigid boxes are made from greyboard (also called chipboard or millboard), a dense board made largely from recycled fibre, wrapped in printed or specialty paper. The structure does not fold flat (except in collapsible designs), which gives rigid boxes their solid, premium feel.

Thickness

Greyboard is usually specified in millimetres:

| Thickness | Feel | Typical uses | |---|---|---| | 1.5 mm | Light but firm | Slim boxes, small accessories | | 2.0 mm | Solid, the usual default | Most gift and retail rigid boxes | | 2.5 mm | Heavy and sturdy | Larger boxes, heavier products | | 3.0 mm | Very solid | Bottles, hardware, premium sets |

Choosing greyboard

Start at 2 mm for most rigid boxes. Go thinner for small, light products, and thicker when the box is large, the product is heavy, or the walls might bow. Very large lids may need thicker board or internal support to stay flat.

Wrap paper

The wrap paper adds little strength but makes a big difference to appearance. Options include coated art paper, uncoated paper, textured and linen papers, leatherette and specialty papers.

How thickness changes box size

Thicker board takes up more space. If your product's inside dimensions are fixed, a thicker board makes the outside dimensions larger. This matters if the box must fit:

• inside a shipping carton
• on a retail shelf or in a display
• within courier size tiers that affect shipping cost

Always tell your manufacturer both the inside size and any maximum outside size.

Thicker is not always better

Thicker board adds cost, weight and volume to every unit and shipment. The right board is the thinnest that protects the product and feels right for your price point. A well-designed structure and insert can often achieve more than simply adding thickness.

Sustainability considerations

• Recycled board such as CRB and most greyboard uses recovered fibre.
• Certified board, such as FSC-certified materials, comes from responsibly managed sources.
• Right-sizing reduces material and shipping impact more than many material swaps.
• Mono-material designs, such as card inserts in card boxes, are easier to recycle.

Food contact and special requirements

If your packaging touches food directly, the board must be suitable for food contact. Recycled boards can contain traces of inks and mineral oils from their previous life, so some food applications need virgin board, a functional barrier or a liner. Products such as frozen food, chilled goods or greasy foods may need coatings for moisture or grease resistance. Ask your manufacturer which grades are suitable for your product and market, and keep their declarations on file.

A quick decision guide

• Retail carton for a light product (cosmetics, supplements, tea): paperboard, around 300 to 400 gsm, SBS or FBB for the best print.
• Retail carton with a natural look: kraft paperboard, with colours designed for brown stock.
• E-commerce mailer: E-flute corrugated, white or kraft, litho-laminated for premium print.
• Shipping box for heavier items: B-flute or C-flute, or double wall for heavy or fragile products.
• Premium gift box: 2 mm rigid greyboard wrapped in printed or specialty paper.
• Large or heavy rigid box: 2.5 to 3 mm greyboard, with inserts or internal supports.
• Rigid box shipped internationally: consider collapsible rigid boxes to save freight volume.

How we help

We make rigid and printed boxes in our own factory and recommend board grades, flutes and greyboard thickness based on your product's size, weight, shipping method and brand. We recommend the board for your product and show the structure on a 3D mockup and digital proof before production.

See our box packaging design and structural and dieline design services, or get a free quote for your boxes.

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Questions

What is the difference between gsm and points?

Gsm measures weight per square metre; points measure thickness in thousandths of an inch. They are related but not interchangeable, because density varies between grades.

What is SBS board?

Solid bleached sulfate: a premium paperboard made from bleached virgin fibre, white throughout, used for cosmetics, pharma and luxury cartons.

Which flute is best for mailer boxes?

E-flute is the most common for retail-style mailers because it prints well and is strong enough for many products. B-flute suits heavier items.

What thickness is a rigid box?

Rigid boxes typically use greyboard from about 1.5 mm to 3 mm, with 2 mm a common default.

Is recycled board strong enough?

For many products, yes. Recycled board can be slightly weaker or less smooth than virgin board, so choose the grade for the product's weight and print needs.

Does board thickness affect box size?

Yes. Thicker board takes up more space, so outside dimensions grow when the inside size is fixed.