Cardboard Box Board Guide | Flute Grades and Paperboard

Board Grades at a Glance

Thickness is approximate and varies a little between mills. Leave it on Not sure yet, describe the contents, and the quote will carry our suggestion with a reason.

Board	Thickness (mm)	Strength	Best for	Print finish
Single wall E flute	about 1.5	Light	Small mailers, postal boxes, retail packs	Very good, sharp print
Single wall B flute	about 3	Medium	Shipping boxes, mailers for everyday parcels	Good
Single wall C flute	about 4	Medium, more cushion	Larger parcels that need some give	Good
Double wall BC flute	about 7	Strong	Heavy, fragile, stacked or palletised goods	Fair, best for 1 or 2 colour
Kraft paperboard	folding grade	Light	Folding cartons, tuck end boxes	Good on natural brown
White paperboard	folding grade	Light	Retail cartons, gift boxes, inserts	Excellent, full colour

What Is Corrugated Board Made Of?

Corrugated board has an outer liner, an inner liner and a fluted paper layer between them. The arches of the flute resist crushing and give the board its stiffness. Single wall has one flute; double wall has two flutes and a third liner.

Which Flute Suits Which Job?

Each letter refers to a flute profile. They are named in the order they were developed, not by size, which is why the letters look out of sequence.

Flute	Character	Typical box
E flute	Thin, smooth, prints crisply	Mailers, postal boxes, retail packs
B flute	Firm, good puncture resistance	Everyday shipping boxes
C flute	Taller arches, more cushion	Larger parcels, softer goods
BC double wall	B and C combined	Heavy, fragile or stacked loads

When Is Paperboard Better Than Corrugated?

Paperboard is a solid sheet rather than a fluted sandwich. It is thinner and smoother, so it folds into neat cartons and takes fine print. Use it for goods that live on a shop shelf or are handed over as presents, not for weighty items sent unaccompanied through a parcel network.

Kraft paperboard: natural brown, suits simple 1 or 2 colour print
White paperboard: bright surface for full colour and photos
Both fold flat and assemble without tape

How Do You Avoid Paying for Strength You Do Not Need?

Start with the lightest grade that will protect the contents, then step up only where the journey demands it. A box that sits inside a larger outer carton can be lighter than one travelling alone.

Note the weight of the packed product.
Decide if the box travels alone or inside an outer.
Consider whether boxes will be stacked or palletised.
Pick the grade from the table above, or ask us to.
If in doubt, ask for two grades on one quote.

Frequently Asked Questions

Sizes and Board

What does single wall mean?

It means one wavy flute glued between an inner and an outer liner, the standard board for most parcels.

What does double wall mean?

It has two waves of fluting and three liners; the usual UK pairing is B with C, sold as BC.

Is C flute stronger than B flute?

C flute is thicker and cushions better, while B flute is firmer against punctures. For most parcels either works well.

Why is E flute used for mailers?

It is thin and smooth, so it folds into neat mailer shapes and prints sharply, while still giving more protection than paperboard.

Does double wall need a different size?

The inside size stays the same, but the outside grows because the board is thicker. We quote on the inside size.

Is thicker board always better?

Not always. Thicker board costs more and adds weight and bulk. The right grade is the lightest one that protects the contents.

What board do folding cartons use?

Solid paperboard in kraft brown or white, which folds crisply and suits retail packaging.

Can I see the board before ordering?

Ask on your quote and we will tell you how to get board samples for the grade we recommend.

Request a Full Quote

Tell us as much as you know. If you are unsure about board or print, leave it on “Not sure yet” and we will suggest the right option with your price.

Board Guide