Boxes 101: Box Type Offerings

What Is Corrugated?

Corrugated fiberboard or "combined board" has two main components: the liner and the medium. Both are made of a special kind of heavy paper called containerboard. Linerboard is the flat material, typically on the outer surfaces of the board but also on the inside for some structures, that adheres to the medium. Medium is the paper that is formed into arches or flutes on the single face and glued between the linerboard facings.


Architects have known for thousands of years that an arch with the proper curve is the strongest way to span a given space. The inventors of corrugated fiberboard applied this same principle to paper when they put arches in the corrugated medium. These arches are known as flutes and when anchored to the linerboard with an adhesive, they resist bending and pressure from all directions, helping to make corrugated boxes one of the best protective packaging solutions on the market.

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When a piece of combined board is placed on its end, the arches form rigid columns, capable of supporting a great deal of weight. The flutes act to keep the linerboard sheets separated, maximizing the bending rigidity of the board. When pressure is applied to the side of the board, the space in between the flutes acts as a cushion to protect the container's contents. The flutes also serve as an insulator, providing some product protection from sudden temperature changes. At the same time, the vertical linerboard provides additional strength and protects the flutes from damage.

Flutes come in several basic designations. Flutes with the same designation have similar size, but may have various flute profiles and number of flutes per foot within a given designation:

  • A flute -  The original flute profile for corrugated board. It has about 33 flutes per foot and is 3/16” in thickness.

  • B flute - Was developed for canned goods that were self-supporting, and so did not require boxes that supported much load. It has about 47 flutes per foot and is 1/8” in thickness.

  • C flute - Was developed next as an all-purpose flute, and it has about 38 flutes per foot and is 5/32” in thickness.

  • E flute - This was the next successful flute profile, and it has about 90 flutes per foot and 1/16” in thickness.

  • F flute - Was developed for small folding carton-type boxes. It has about 125 flutes per foot and is 1/32” in thickness.

In recent years not only has there been a proliferation of flute profiles, but there has been an increase in the variation in flute characteristic measurements for any given flute profile. Flute profiles will vary, sometimes significantly, because the corrugator rolls are manufactured to address a variety of aspects (such as speed, paperboard characteristics, economies, etc.).

Combined Board

The below illustration demonstrates four basic types of the combined board that are most commonly created from linerboard and medium using a variety of flute structures:

  • Single Face: One corrugated medium is glued to one flat sheet of linerboard.

  • Single Wall: The corrugated medium is glued between two sheets of linerboard. Also known as Double Face.

  • Double Wall: Three sheets of linerboard with two mediums in between.

  • Triple Wall: Four sheets of linerboard with three mediums in between.

Generally, larger flute profiles deliver greater cushioning and vertical compression strength, while smaller flute profiles provide enhanced graphics capabilities. Smaller flutes such as E and F also provide enhanced structural capabilities for primary (retail) packaging compared to paperboard (folding cartons). There is a good deal of variance across the industry in the range of flute sizes based upon the container characteristics that are desired for each application, as well.

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Corrugated Box Weight Limits

What Factors Affect the Strength of Corrugated Boxes? 

There are several factors that affect the overall strength of corrugated boxes. This includes

  • The paper type used in the liner board
  • The fluting profile
  • The thickness level of the base paper used in the liner board and fluting

The weight and type of paper combined play a crucial role in a corrugated box's ability to withstand the weight of other packages in transit. 

The corrugated packaging weight class that you need depends on the types of products you need to ship. Luckily, every weight class can be ordered in bulk or small volume, meaning we have you covered no matter what packaging solutions you may need. 


Extreme Lightweight

Boxes for very basic items that you are not worried about getting crushed or taking stacking damage can be made from a single face corrugated. Single face board includes one corrugated medium glued to one flat sheet of liner board, leaving the flutes visible on the inside and making the material easy to wrap around items. 

If you are looking for a lightweight box between single face wrap and the standard single-wall 32 ECT box, a 26 ECT box can hold up to 35lbs. 


Up to 65 Pounds 

Once you start to have concerns about box strength or plan to ship your boxes to other businesses and consumers, 32 ECT comes into play. 32 ECT and 200# Mullen single wall boxes are the most standard corrugated boxes, with the ability to hold up to 65 lbs. This makes them a perfect B2B packaging solution.

Constructed from one corrugated medium which is glued between two sheets of liner board for added strength, they come in a variety of sizes to meet your packing and shipping needs. 


From 66-95 Pounds

Here at 66-95 pounds, you are starting to get a little more serious about the weight of the product inside your box. You want a heavy-duty single-wall box that is able to withstand the added weight while being handled, shipped, and stored. That means you’ll want to begin using a 275# Mullen or 44 ECT box. 


From 86-100 Pounds

Although some single-wall corrugated boxes can capably hold up to 120 pounds, this range is generally considered the tipping point where you want to start thinking about double wall construction for added durability. Double-wall means that there are three sheets of liner board with two mediums in between, making two “walls” and greatly increasing the box strength. 

Standard entry-level double wall boxes are 48 ECT or 275# Mullen.


From 101 to 120 Pounds

The next strongest box is 51 ECT or 350# Mullen double-wall, using a stronger liner board to hold up to 120 pounds. 


From 121 to 280 Pounds

As the weight of your shipment increases, the chances are that its value or specificity will increase immensely as well. This is no time to skimp  on the packaging; instead, it is the time to call in the big guns –triple wall corrugated. Triple wall is often considered a replacement for wooden crates and other custom-built, high-cost packaging methods. 

Here, four sheets of liner board are constructed with three mediums in between, making 3 “walls” for maximum toughness. With their triple layer of protection, these corrugated boxes are rated 400# up to 1100# on the burst test and from 61 ECT up to 90 ECT.


From 281 to 300 Pounds

The largest and heaviest of corrugated boxes can withstand up to 1300# on the bursting test and carry an ECT of 155. Extra reinforcements may be used such as the carton being stitched (stapled shut rather than glued shut), or adding wood to the floor of the carton. 


Corrugated Board Strength Charts

V2_Corrugated_Board_Strength_Charts (1)Aside from the ability to hold many different weights, corrugated boxes are one of the best industrial packaging solutions thanks to their ability to protect your products, customize your brand, and keep your total costs low (not to mention the environmental perks).

 The possibilities are endless, from the lightest to the heaviest of items there is a corrugated box that will cradle your product safely from start to finish!


Most industries have a standard for measuring or describing the construction of a particular material. However, in the corrugated industry, there are two standards – the Mullen Test and the Edge Crush Test. This leads to quite a bit of confusion in the marketplace.

The Mullen Test, which has been used for many years, tests the bursting strength of corrugated board – how much pressure is required to rupture the wall of a piece of corrugated material. Boxes conforming to the Mullen Test standard are identified as 200# Test, 275# Test, etc. The higher the number, the stronger the corrugated box.

The Edge Crush Test, which was developed in the 1990s, measures the stacking strength of corrugated board – how much top-to-bottom pressure a box can withstand before crushing. Boxes conforming to the Edge Crush Test standard are identified as 32ECT, 44 ECT, etc. Again, the higher the number, the stronger the corrugated box. For most general-purpose applications, 200# Test and 32ECT are interchangeable; however, the board comprising 200# Test material is slightly heavier than the 32ECT equivalent, making it somewhat more expensive. 32ECT boxes have become extremely popular since the Edge Crush Test was introduced, partly due to cost, and partly because stacking strength is a more meaningful measure of how a box will perform in the field.


·         Tests the bursting strength of corrugated board – how much pressure is required to rupture the wall of a piece of corrugated material

·         The higher the number, the stronger the corrugated box

·         Costs more than the Edge Crush Test equivalent

·         Most common grades: 200#, 275#, and 275# doublewall

·         More stiff than its Edge Crush Test equivalent due to slightly heavier board combination

Edge Crush Test (ECT)

·         Measures the stacking strength of corrugated board – how much top to bottom pressure a box can withstand before crushing

·         The higher the number, the stronger the corrugated box

·         Costs less than the Mullen equivalent

·         Most common board grades: 32ECT, 44ECT and 48ECT doublewall

·         The most popular choice due to best price and sustainability while still offering adequate protection during shipping


Mullen Test & ECT Liner Combinations

 Box Style

Boxes can be used to ship everything from apples to washing machines. By changing the design of a box, combining layers of corrugated or adding interior packaging, a corrugated box can be manufactured to efficiently ship and store almost any product.

Many standard box styles can be identified in three ways: by a descriptive name, by an acronym based on that name, or by an international code number. The numerical code system, known as the International Fiberboard Case Code, was developed by the European Federation of Corrugated Board Manufacturers (FEFCO) in collaboration with the European Solid Board Organization (ESBO) to avoid confusion when communicating in different languages.

Below are some common box style categories and designs. Keep in mind there are many other standard styles from which to choose. In addition, corrugated boxes can be custom-designed to meet the specific needs of any box user. A manufacturer's representative will have more information about additional box style options.

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Have Questions? We've Got Answers!

No matter what industry you're serving, developing custom-use packaging for your products lowers the chances of damaged goods and ensures you're not overspending on shipping costs.  -- Have questions about what type of packaging will work best for your application? Check out one of our free resources below: 

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Your product left the warehouse and is on its way to your customer. They’re eagerly waiting for it to arrive at their front door. But when it does, will it be in
one piece?

While you can’t control every aspect of the shipping process, custom protective packaging helps ensure a good unboxing experience for your customers.

This guide will cover:
Why Custom Protective Packaging Matters
Protective Packaging Considerations
Types of Protective Packaging Materials

Download the Protective Packaging Guide