Corrugated 101

Published on Mon, Apr 17, 2023 4:00 PM GMT


Corrugated cardboard (or simply, corrugated) is a product essential to many industries with applications ranging from packaging, pallet liners, signage, stiffeners, and dividers, to picture frames and other endless possibilities.


Corrugated contains varying layers of kraft paper with an interior layer of paper (also known as a corrugated medium) that provides the cardboard with durability and strength. The inner sheet undergoes a corrugation process to be turned into folds, or flutes. The arched curves in the flutes are essential in preventing excess damage to protected items, as they add durability and resistance to pressure from any applied angle. The spaces between the flutes and arches also provide cushioning and insulation when working with extreme temperatures.  The corrugated medium is then glued between the two sheets of kraft paper. This forms a multi-layered structure that is more durable than standard cardboard.


Types of Corrugated

There is a multitude of different types of corrugated that provide varying levels of thickness and strength based on your needs.

Corrugated can be categorized into the following most common board styles:

  • Singleface – Made of two layers only: A liner layer and a corrugated layer, and is usually sold in rolls as opposed to sheets

o   Common uses: Interior packaging, wrapping items, cushioning within boxes

o   Does not have as much durability as other types of corrugated

  • Single Wall – The most common form of corrugated, consists of two outer liners and a corrugated middle layer (this is what pretty much all corrugated boxes are made of)

o   Common Uses: Shipping cartons

o   If someone mentions corrugated cardboard, they are most likely referring to this style

  • Double Wall – Contains two layers of corrugated fluting and three liners  

o   Common Uses: Heavy-duty industrial cartons

o   Extremely durable

  • Triple Wall – Strongest face type, contains four layers of liners and three layers of fluting

o   Common Uses: Shopping crates, chemical containers

o   Strong enough to replace wooden crates

o   Reliable for shipping chemicals or other items that require special handling  

The following diagram shows examples of the different types of corrugated:


Corrugated Flute Styles

Corrugated cardboard also has varying types of fluting, each with its own letter designation including letters A, B, C, E, and F.

A Flute (1/4” thick): Excellent compression and cushioning, and provides good stacking strength.

  • Common Uses: Packaging fragile items for its structural strength

B Flute (1/8” thick): Offers great crush and puncture resistance and is a good printing surface.

  • Common Uses: Inner packaging components including pads and partitions

C Flute (5/32” thick): Has very good crush resistance, compression properties, and is also a great printing surface.  Approximately 80% of boards and boxes make up this flute size.

  • Common Uses: Shipping boxes to secure food, glass, furniture, etc.

E Flute (1/16” thick): A thin flute style that reduces storage space while providing crush resistance and acts as an ideal printing surface

  • Common Uses: Packaging consumer goods including glass/ceramics/cosmetics, displays, pizza boxes, ballot boxes

F Flute (1/32” thick): The thinnest type of corrugated and is also sometimes referred to as microflute, it has the best printing surface and a high-level crush resistance because it is relatively dense  

  • Common Uses: Fast food clamshell containers, packaging consumer goods including shoes/jewelry/cosmetics

Corrugated Cardboard is only one product amongst the largely extensive paperboard family. While paperboard comes in varying shapes and sizes, it is all measured using two types of systems.  

Imperial Measurement System

The Imperial Method measures the thickness of a board in thousandths of an inch and is expressed using “x point” (ie. 20 point/.020 which is .020” thick or 90 point/.090 which is .090” thick).

Metric Measurement System

The Metric Method measures the thickness of a board in millimetres. An equivalent conversion to imperial measurements would be 1 mm for every 40 point (.040” thick) board.


Measuring Corrugated Cardboard Strength (Mullen Burst Test)

Many paperboard professionals use the industry standardized Mullen Burst Test to ensure that corrugated boxes can withhold pressure from external forces and maximize the protection of their inside products.

The Mullen Burst Test involves a pressurized diaphragm that measures the amount of pressure (in pounds/square inch) the side of a corrugated box can take before rupturing. This test is most valuable in scenarios where you are shipping items that move in the corrugated box (plastic beads, ball bearings, round fruit, etc.), or where boxes are being unloaded multiple times throughout the transport.

In standard single-wall corrugated, the Mullen Burst Strength measurements would normally be from 23 to 32, with a 32 being a stronger more durable sheet and a 23 being a less strong sheet.

As you will note if you get a quote for corrugated cardboard, the Mullen Burst Test strength is one of the variables in the specification.  For example, if you were buying corrugated sheets, you might get a quote that appears as follows: 

26C corrugated 40x48

In this case:

26 is a measure of the strength of the cardboard (as per the Mullen Burst Strength test);

C is the measure of how thick the sheet is; and

40x48 is the sheet size (usually measured in inches).


Contact Us

Operating out of Vaughan, Ontario, Hammond Paper Company has been a reliable source for corrugated, chipboard and other paperboard products and converting in Canada for over 30 years.  Whether you’re looking for standard size sheets or custom sheets or packaging, Hammond Paper can help.  We’re not just about board – we can do custom laminating, cutting to size, die-cutting, round cornering, grooving and more.


Call us at (905) 761-6867 or email us at to get a free quote or to get more information.