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Corrugate material uses a layering technique that reinforces boxes and makes them stronger for shipping and storage.

Corrugate: The Basics

A liner (flat paper) is glued and pressed to fluting (wavy paper), creating single face corrugate. This is the base for what will become sheeting, rolls and boxes. Extra layers of liners and different sizes of flutes can increase corrugate’s strength and support.

Corrugate or Cardboard?

If you find yourself calling a packing or shipping box a cardboard box, you’re not alone. Cardboard is now so common that most people use that word when talking about any kind of box. But when it comes to boxes and their construction, the difference between corrugate and cardboard is a simple but important one.

Cardboard is a thick paper stock (also called paperboard) used for creating attractive packaging and its inside dividers or lining. Typically it’s used for food packaging like cereal boxes, small electronics like cameras, and even entertainment products like playing cards and board games. Basically, if it sits on a shelf and needs to look great, it’s packaged in cardboard.

Corrugate material uses a layering technique that reinforces boxes and makes them stronger for transporting and storing items. Corrugate boxes are used to protect large goods like televisions, ship multiple products in one box, or even deliver a hot and delicious pizza (meat lovers, FTW!). If it needs to be protected from possible damage, corrugate is the way to go.

Corrugate: Board Strength

Board strength is created by flute size and the number of box walls used. This determines how strong a box will be once assembled. When choosing board strength, look at  what will be packed in the box, the total weight of the box and its contents, the size of the box itself and how it will be stacked and shipped.

Corrugate: Box Strength

Edge Crush Test (ECT) measures the stacking strength of a box. This determines how much pressure it can handle before being crushed. Since most shipping is done on skids, this is the modern world’s ideal strength test.

Mullen Test measures the wall strength of a box. This determines how much pressure it takes to puncture or rupture a box wall (hence its other name, the burst test). Thanks to modern day shipping and the use of ECT boxes, the Mullen test has become less relevant.

The Packaging Company uses ECT when measuring box strength. In today’s word of e-commerce, ECT-rated boxes have what it takes to make sure your parcels reach their final destination intact.

Corrugate: Board & Flute Styles

corrugate box walls

Single Face corrugate is a layer of sheeting and fluting. It’s easy to fold or roll and is used in packaging to keep items separated from each other.

Single Wall corrugate is fluting sandwiched between two layers of paperboard. This is the most common board style, perfect for standard box sizes and shipping needs.

Double Wall corrugate adds an extra layer of fluting and paperboard to single wall corrugate. This makes it ideal for heavier or more delicate items.

Triple Wall corrugate adds another layer to double wall corrugate.  This provides the strength needed to protect much larger and heavier items during transit.


corrugate flute sizes

A Flutes have roughly 30 flutes per foot and are 3/16th of an inch thick. This creates greater strength and cushioning for shipping heavier items.

B Flutes have about 45 flutes per foot and are 1/8th of an inch thick. This improves stacking strength for boxes and crush resistance for things like product displays.

C Flutes have around 40 flutes per foot and are 11/64th thick. They’re the most commonly-used size, covering the difference between A and B flutes.

E Flutes have about 90 flutes per foot and are 1/16th thick. This reduces box size and saves on storage space since the box profile is incredibly thin. They’re perfect for printing and die-cutting.

F Flutes have around 125 flutes per foot and are 1/32nd of an inch thick. They have excellent foldability and a great surface for printing on.

Corrugate: How to Measure a Box

corrugate box dimensions

Length x Width x Height is the correct way to measure a box. Length is the longest horizontal measurement, Width is the shortest, and Height is the vertical measurement.

When you’re measuring a box, there are two other dimensions that you should know.

Inside Dimensions are the inner measurements of a built box. A box listed as 12″ x 12″ x 12″ is referring to the space inside it. This is called the usable cube. When you’re purchasing boxes, make sure you know the actual space you’ll need to properly fit your items.

Outside Dimensions are the outer measurements of a built box. That 12″ x 12″ x 12″ box is larger on the outside because of the corrugate wall’s thickness. This is important to know when you’re shipping through a mail carrier. They go by dimensional weight (the outside dimensions and weight of the box), and choosing the right box can save you money on shipping charges.

Corrugate: How to Read a Box Maker’s Certificate

A Box Maker’s Certificate (BMC) is a seal printed on the bottom of a box that tells you how strong it is. It’s not legally required, but it’s proof that the box has been properly tested and rated.

corrugate bmc

Corrugate: Words Worth Knowing

Die-Cut is the design or shape cut out from corrugated material using a die. It’s then used to create displays, boxes and interior packaging.

Flutes are sheets of wavy paperboard that create support and cushioning in box board. Different sizes of fluting allow for different uses of box board.

Headspace is the area inside a box between the top of a product and the sealed box top. Void Fill should be used to stop the product from moving around.

Kraft is what liner is often made from. Wood fibers are turned into pulp, paper and paperboard, which become boxes, wrapping paper, void fill and more.

Liners are sheets of paperboard glued to sheets of fluting to create box board of varying strengths and thicknesses.

Medium is another word for flutes, the wavy paperboard used in corrugated material.

Multi-Depth Boxes have several score lines on box walls to create a perfect fit for a shipped item. This helps prevent damage and avoid use of excess void fills.

Paperboard is used in creating corrugated and cardboard boxes.

Rolled Corrugate is a singleface or single wall layer of corrugate. It’s highly scored so it can be rolled up for storage or used to wrap delicate items.

Score is a machine-made depression that makes the folding and shaping of corrugate easier.

Telescoping Boxes are a two-piece box in which one part (usually the top) fits over the other. This is often used in mailing tubes and smaller boxes meant for products worth displaying.

Usable Cube is the space inside of a built box that can be used for shipping and packing.