Cardboard Box Types: Which Grade And Style Do You Need?

Choosing the right cardboard box for your products isn't about stuffing them in and hoping for the best. Not all cardboard boxes are the same, and two boxes can be the same size and still perform completely differently once your products are inside and en route to their destination.

When it comes to choosing a cardboard box, the difference comes down to three things:

• How many layers of fluting the board has
• The size of the flutes
• The style of the box

Get those right, and your products arrive in one piece. Get them wrong, and you'll either pay for a stronger box than you need or deal with damaged stock and returns.

What are the different types of cardboard?

The word cardboard is used for a few different materials, so it's worth knowing which one you actually need for your products.

• Corrugated board: A wavy, fluted layer glued between two flat liners. It's used to make shipping boxes, postal boxes and most storage boxes, and it's what we make at Fastbox.
• Carton board: A thin, flat board used for things like cereal boxes and retail cartons. It looks good on a shelf, but it isn't designed to protect heavy or fragile products.
• Greyboard: A thick, rigid board that is often used for luxury gift boxes and book covers.

If your products need to be shipped, stacked or stored, you'll want corrugated board. It’s made by gluing fluted paper between flat liners, which is what makes it strong enough to ship and stack

Single wall, double wall, or triple wall cardboard boxes?

The number of walls tells you how many fluting layers are in the board. The more layers a box has, the stronger and thicker it is, but also the heavier and more expensive.

• Single Wall Cardboard Boxes: Made up of one layer of fluting between two liners. These boxes are perfect for light, non-fragile items, postal and storage boxes.
• Double Wall Cardboard Boxes: Made from two layers of fluting and three liners. They're used for heavier or more fragile items, boxes that will be stacked on top of each other and for longer journeys to the customer.
• Triple Wall Cardboard Boxes: Made from three layers of fluting. These are used for very heavy industrial loads and export shipping. For most businesses, double wall boxes will do the job.

If you're unsure which box to choose, you need to think about the heaviest product that will go in the box and the roughest part of its journey. A box that only travels across the city to your customer is very different from one going through a depot or being stacked on pallets.

What do flute sizes mean?

The flutes are the waves in the middle of the board. Flute sizes are given letters, and each one does a slightly different job. But as a rule of thumb, thinner flutes give you a smoother surface for printing, while thicker flutes give you more cushioning and strength.

The letters come from the order the flutes were invented, not their size, which is why they can be confusing to understand. So here is everything you need to know:

• E flute (about 1.6mm): Thin, with a smooth surface that takes print well, which is why it's often used for mailer boxes and retail packaging.
• B flute (about 3mm): Still fairly thin but has good crush resistance and is commonly used for single wall boxes.
• C flute (about 4mm): Thicker, with more cushioning and better stacking strength than the thinner flutes.
• A flute (about 5mm): The thickest of the standard flutes and comes with the most cushioning.
• BC flute (about 7mm): This combines the B flute and C flute to make double wall board. It's one of the most common combinations for heavy-duty double wall boxes.

What do liners and board grades mean?

The liners are the flat layers on the outside of the board. Kraft liner is made mainly from fresh wood pulp and is the strongest option. Test liner is made from recycled paper and suits most everyday boxes.

You'll often see the board listed as a code on product pages, like the 125KT on our single wall boxes. The number is the grammage, or GSM, which stands for grams per square metre. The K means the outer liner is kraft paper, and the T means the inner liner is testliner, the recycled option.

The higher the number, the heavier and stronger the liner. Our standard single wall boxes use 125KT, while boxes like our BDCM range use a heavier 150KT.

Kraft paper sits on the outer layer because it's the strongest liner and the best to print on. There are four main types of kraft liner:

• Classic brown kraft.
• White top kraft.
• Fully bleached kraft.
• Mottled kraft.

Finally, testliner is a duplex paper made mainly from recycled fibres, and it's usually used for the inner liner of the box. It comes in different grades, with Test 1 being the strongest:

• Test 1: The strongest testliner grade.
• Test 2: A mid-range grade, sometimes called an enhanced testliner.
• Test 3: A lower-strength grade made from fully recycled fibre.

Common cardboard box styles

The style is the shape of the box and how it opens and closes. These are the styles most businesses use in the UK:

Standard slotted boxes: The box most people picture, with four flaps on the top and bottom that meet in the middle. In the packaging industry, this is known as FEFCO 0201, and it's the most common style for shipping and storage.

• Letterbox Mailers: Slim boxes with a tuck-in lid that fit neatly into household letterboxes. They're suitable for slim, non-bulky items and promotional materials.
• BDCM Boxes: Standardised cartons designed to suit common footprint sizes. They help retail and ecommerce businesses cut down the number of box sizes they hold.
• Archive Boxes: Boxes with separate or hinged lids, perfect for document storage and file organisation. With a simple assembly method, they're quick and easy to put together.
• Pallet boxes: Large boxes that sit on a pallet, used for bulk and heavy goods.
• Die-cut boxes: Any box cut to a custom shape, with built-in features like locking tabs, handles or inserts.

How to choose the right type of cardboard box for your products

Ask yourself these five questions before you order any boxes:

• How heavy is your product? The heavier it is, the stronger the board needs to be.
• Is it fragile? Fragile items need more cushioning, either from a thicker flute or from protective packaging inside the box, such as the packing materials that work best for shipping.
• How far is it travelling? Boxes going through courier networks get handled far more than boxes delivered locally.
• Will it be stacked? Boxes stacked on pallets or in your warehouse need stronger board to stop the bottom ones from crushing.
• Does it need to look good? If the box is part of your customer's experience, a smoother flute will give you a cleaner print.

Standard boxes or custom boxes?

If your products fit well in a standard size, a stock box is usually the quickest and cheapest option. If your products are an unusual shape, move around inside standard boxes or need printing, a custom box will often save you money and help you avoid damaged products.

Get your dimensions right first, then put a custom box together in our Box Builder. But if you're unsure about a new design, you can order a trial run and test it with a smaller batch of products first.

Common mistakes when choosing cardboard boxes

Choosing the right cardboard box sounds simple, but a lot of businesses still get it wrong. These are the mistakes we see most often and the ones you need to avoid making:

Choosing the wrong wall

Using single wall boxes for heavy products is one of the most common reasons boxes split or crush. But don't use double wall boxes for everything either, as you'll be paying for more board than you need.

Ordering the wrong size box

The fit matters just as much as the strength. Too much space and your product could rattle around and leave you needing to fill up space. But too tight and you risk crushing the product while packing, or putting pressure on the seams and corners, which is usually where boxes break.

Holding too many box sizes

Every extra box size means more stock to store and more chance of your team packing with the wrong one. Standardising on fewer sizes, like the BDCM range, keeps things simpler.

Cardboard boxes from Fastbox

Every box type on this page, from single wall and double wall to BDCM, archive and pallet boxes, letterbox mailers, printed boxes and die-cut packaging, is made in our own factory in Leeds. 

Orders start at 10 boxes using stocked materials, and there’s more on our capacity, lead times and stockholding if you’re planning a bigger run.

Not sure which type of cardboard box you need? Ring us on 0113 277 9511 or email sales@fastboxpackaging.co.uk. Tell us what's going in the box and where it's going, and we'll point you in the right direction.

Cardboard box types frequently asked questions

Does it matter what kind of box you use to ship?

Yes. The wrong board grade or the wrong size is the most common reason products get damaged. A light product going a short distance can go in a single wall box, but anything heavy, fragile or going through a courier network will usually need double wall boxes.

Which flute is best for shipping boxes?

It depends on your product. B flute and C flute are the most common for single wall shipping boxes, while BC flute double wall board is used for heavier or more fragile items. E flute is better suited to lighter mailers where print quality matters.

How much weight can a cardboard box hold?

There's no single answer, as it depends on the board grade, the flute, the size of the box and how it's packed and stacked. As a rough guide, single wall suits light items and double wall suits heavier items.

Is kraft or test liner better?

Kraft liner is stronger and better to print on, so it's usually used on the outside of boxes. Test liner is perfectly good for most everyday boxes. A lot of boxes use kraft on the outside and test liner on the inside to get the best of both.